SQL basics€¦ · SQL basics INDEX S.No Topics Page number 1 Creating and altering table...

SQL basics INDEX

S.No Topics Page number

1 Creating and altering table records(DDL and DML) 2

2 Constraints 7 3 Joins 13 4 Views 16

5 Control flow constructs in SQL 18 6 Using Local Variables 20 7 Cursors 21 8 Creating User Defined Data types 28

9 Stored Procedures 28 10 Functions 33 11 Exception Handling in Procedures 40 12 Triggers 44

13 Indexing in SQL 52 14 Transaction and Locking 55 15 XML support in SQL Server 60

Trainer: Mr. C.Santhosh Kumar,

329649.

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1.Creating and altering tables --Creating a Database

Syntax: create database database_name

Create database dn016_346238

--using database

Syntax: use database_name

use dn016_346238

--creating schema

Syntax: create schema schema_name

create schema cts

--creating table

create table employee

(

id int primary key,

name varchar(50),

address nvarchar(max),

mail_id nvarchar(50)

)

--inserting values to table

insert into cts.employee values(346238,'prasanna','tiruvannamalai','[email protected]')

insert into cts.employee values(346197,'lakshman','salem','[email protected]')

insert into cts.employee (id,address) values (346200,'tiruvannamalai')

--Displaying all entries in the table

select * from cts.employee

--adding new column to the table (Altering the table data structure)

alter table cts.employee add phone int

--Altering an existing column

alter table cts.employee alter column cell nvarchar(15)

--updating name with the given ID.

update cts.employee set name='lena prasanna' where id = 346238

update cts.employee set cell='9952941393' where id = 346238

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--renaming a particular column name in the table

exec sp_rename 'cts.employee.phone','cell','column'

--displaying top 2 records in the table

select top 2 Id,name from cts.employee

--displaying selected entries based on the conditions given

select * from cts.employee where name='lakshman' and address='salem'

--creating another table

create table cts.employees

(

empid varchar(10) primary key,

empname varchar(200),

deptid varchar(10),

joining_date date,

dob date,

yrs_of_expr int,

employee_category varchar(10)

)

--displaying all the entries in the table

select * from cts.employees

--inserting values to table

insert into cts.employees values(346238,'lena','dn','2012-08-28','1990-05-09',0,'programmer analyst

trainee')

insert into cts.employees values(346200,'kishore','dn','2012-08-28','1990-12-08',0,'programmer analyst

trainee')

insert into cts.employees values(346201,'prasanna','dn','2012-08-28','1990-07-10',0,'programmer

analyst trainee')

insert into cts.employees values(346197,'lakshman','dn','2012-08-28','1990-08-16',0,'programmer

analyst trainee')

--adding new column to the table (Altering the table data structure)

alter table cts.employees alter column employee_category varchar(50)

--displaying details based upon a condition

select empid,dob,joining_date from cts.employees where (year(joining_date))>2010 and

(month(dob))>5

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--counting no. of records in the employee table based upon a specified condition

select COUNT(*) "no,ofemployees" from cts.employees where (year(joining_date))>2010 and

(datename(mm,dob))='december'

--Displaying all entries with the difference between 2 dates is greater than 21

select empid,dob,joining_date from cts.employees where DATEDIFF(yy,dob,joining_date) >21

--Deleting a specific entry from table

DELETE FROM cts.Employees where dob='1990-07-10'

--T- SQL Operations

Select , Order by, from, where clauses:

o SELECT keyword is used to display all the entries specified next to it.

o ORDER BY clause allows us to sort the records in your result set. The ORDER BY clause can

only be used in SELECT statements

o FROM clause produces the tabular structure, the starting set of data on which all other

operations in a SELECT statement are performed. Note that, FROM clause is the first clause

that will be looked by the database system while parsing the SQL statement. o WHERE clause is always followed by the condition. It is used to filter the data set.

o Syntax :

SELECT columns

FROM tables

WHERE predicates

ORDER BY column ASC/DESC;

Top clause:

o TOP clause is used to specify the number of records to return.

o Syntax:

SELECT TOP number|percent column_name(s)

FROM table_name

Patterns and wildcards:

o SQL patterns and wildcards can substitute for one or more characters when searching for

data in a database.

o For example:

o ‘%s’ - displays all the strings that ends with ‘s’

o ‘s%’ – displays all the string that starts with ‘s’

o ‘%san%’ – displays all the strings that has ‘san’ either in the front or at the back

o ‘[san]%’ – displays all the strings that starts with s,a, and n.

o IN CLAUSE in SQL is typically used in a WHERE clause. It is normally used when we want to

create a subset of records from another set.

o BETWEEN clause is used to select a range of values specified between the keyword

‘between’ & ‘and’.

o '_00%' - Finds any values that have 00 in the second and third positions.

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o The below is the table which gives more explanation about the wildcards.

Wild card Description

% A substitute for zero or more characters

_ A substitute for exactly one character

[charlist] Any single character in charlist

[^charlist] (Or) [!charlist]

Any single character in charlist

Note: LIKE clause is used to compare a value to similar values using wildcard operators. There are two wildcards used in conjunction with the LIKE operator:

The percent sign (%) The underscore (_)

String Functions:

There are some inbuilt functions in SQL that will be used to manipulate the strings. They are as

follows:

a) substring(string,startIndex,length) - Returns part of a string. For example, SELECT

SUBSTRING('SQLServer', 4, 3) returns ‘Ser’.

b)len(string) – returns the length of the string. For example SELECT LEN(‘Hello’) returns 5.

c)upper(string) – Converts the given string to uppercase.

d)lower(string) – Converts the given string to lowercase.

e)replace(string1,String2,String3) -Replaces all occurrences of the string2 in the string1 with string3. For

example, SELECT REPLACE('All Function' , 'All', 'SQL') will return ‘SQL Function’

f)ltrim(string) and rtrim(string) – ltrim(String) returns a string after removing leading blanks on Left side.

For example, SELECT LTRIM(' sqlserver') returns 'sqlserver' (Remove left side space or blanks).similarly,

rtrim(String) Returns a string after removing leading blanks on right side. For example,

SELECT RTRIM('sqlserver ') returns 'sqlserver' (Remove right side space or blanks).

g)left(String,Integer) - Returns left part of a string with the specified number of characters. For example,

SELECT LEFT('TravelYourself', 6) gives ‘Travel’

h)right(String,Integer)- Returns right part of a string with the specified number of characters. For

example, SELECT RIGHT('TravelYourself', 6) gives ‘urself’

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Date Functions:

There are several functions that deals with date manipulation.They are:

a)Getdate() and sysdatetime() –returns current date and time from the sql server

b)Dateadd(format,number,date) - adds or subtracts a specified time interval from a date.

c)Datediff(format,date1,date2) - returns the time between two dates.

d)Datepart(format,date) -returns a single part of a date/time, such as year, month, day, hour, minute,

etc.

e)Datename(format,date) - returns the name or value of the specified datepart of the a date.

format – yy/yyyy/mm/dd/d/m/ hh/mi/ss

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2.CONSTRAINTS Points to remember:

Constraints are used to limit the type of data that can go into a table.

Constraints can be specified when a table is created (with the CREATE TABLE statement) or after the table is created (with the ALTER TABLE statement).

There are several constraints available in SQL. They are namely,

a)Primary key d) Default

b)Foreign key e) Unique

f)Not null

Defining Primary key constraint:

o Creating a column as a primary key:

Syntax:

Create table tablename

(

Columnname type primary key,

……

)

Note: If we add primary key constraint as said above, then we will not be

able to drop them individually. Instead, we need to drop the entire table

later if there is a change in the primary key column of the table.

o Creating a primary key constraint at column level:

Syntax:


(

Columnname type constraint constraint_name primary key,

……

)

Note: If we add primary key constraint as said above, then we can drop the

primary key constraint whenever needed without needed to drop the table.

o Creating a primary key constraint at table level:

Syntax:


(

Columnname1 type1,

Columnname2 type2,

……,

ColumnnameN typeN,

Constraint constraint_name primary key(columnnameN)

)

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o Adding primary key constraint using ‘alter’ DDL command:

Syntax:

Alter table tablename add constraint constraint_name

Primary key(col)

Defining Foreign key constraint:

o Creating a column as a foreign key:

Syntax:


(

Columnname type foreign key references constraint_name (pk_column),

……

)

Note: If we add foreign key constraint as said above, then we will not be able

to drop them individually. Instead, we need to drop the entire table later if

there is a change in the foreign key column of the table.

o Creating a foreign key constraint at column level:

Syntax:


(

Columnname type constraint constraint_name foreign key references

Pk_table_name (pk_column) ,

……

)

Note: If we add foreign key constraint as said above, then we can drop the

constraint whenever needed without needed to drop the table.

o Creating a foreign key constraint at table level:

Syntax:


(

Columnname1 type1,

Columnname2 type2,

……,

ColumnnameN typeN,

Constraint constraint_name foreign key(columnnameN) references

Pk_table_name (pk_column),

)

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Note: If we add foreign key constraint as said above, then we can drop the

constraint whenever needed without needed to drop the table.

o Adding foreign key constraint using ‘alter’ DDL command:

Syntax:


Foreign key(column_name) references

Pk_table_name(pk_column)

Defining Check Constraint:

o Creating a column as check constraint:

Syntax:


(

Columnname type check(condition),

……

)

o Creating a check constraint at column level:

Syntax:


(

Columnname type constraint constraint_name check(condition),

……

)



o Creating a primary key constraint at table level:

Syntax:


(

Columnname1 type1,

Columnname2 type2,

……,

ColumnnameN typeN,

Constraint constraint_name check(condition)

--Note: Like primary key and foreign key constraint, There is no need to add

extra column name for check constraint as the condition given to check

constraint will be a column name.

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Defining Default constraint:

Syntax:


(

Columnname1 type1 default value1,

Columnname2 type2 check(condition) default value2,

--Note: We can also combine check constraint with the default constraint.

….

)

Defining default constraint using alter command:

Syntax:


Default default_value for column_name

Using in table level:

o Syntax:


(

Column1 type1,

Column2 type2,

….

Constraint constraint_name default default_value for column

)

To drop any constraint:

o Syntax:

Alter table tablename drop constraint constraint_name

--using database

use 346238

--check if the table is already exist, if exist, drop the table.

if OBJECT_ID('cts.Customer','U') is not null

drop table cts.Customer

--creating table

create table cts.Customer

(

c_id int,

c_name varchar(50),

address varchar(max),

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constraint pkey primary key(c_id)

)

--check if the table is already exist, if exist, drop the table.

if OBJECT_ID('cts.orderid','U') is not null

drop table cts.orderid

--creating table

create table cts.orderid

(

orderno int constraint p_key primary key,

--If we use orderno int primary key, we cant modify. if we add it as a constraint, we can drop anytime we

--want to. So we used "orderno int constraint p_key primary key"

product_name varchar(50),

c_id int

)

--Alter table definition by adding new column

alter table cts.Customer add language_known varchar(50)

alter table cts.orderid add Product_Qty varchar(50)

alter table cts.orderid add Order_Price money

--Alter table to add constraint

alter table cts.orderid add constraint f_key foreign key (c_id) references cts.Customer(c_id)

alter table cts.orderid add constraint def_key default 1000 for orderno

alter table cts.orderid add constraint check_key check (orderno>500)

--alter table syntax to drop constraint

alter table cts.orderid drop constraint def_key

alter table cts.orderid drop constraint f_key

--inserting values into the table

insert into cts.Customer values ('Kishore', 'Tamilnadu','Tamil');

insert into cts.Customer values ('Lenaprasanna','Andhrapradesh','Telugu');

insert into cts.Customer values ('Chanakya','Andhrapradesh','Telugu');

select * from cts.Customer;

--DDL command that deletes all the entries from the table

truncate table cts.orderid;

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--Constraints usage

insert into cts.orderid values (1002,'Dictionary',1000,1,100.00) -- it will not get inserted as it violates

check constraint. Recall that, Check constraint condition is orderno > 500

insert into cts.orderid values (1000,'E-Learning',1002,3,5000.00) -- it will be inserted.

select * from cts.orderid

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3.JOINS

Concept:

Querying result from multiple tables is the main concept of Joins.

It provides new visualized table records.

There are 3 types of join. Namely:

1.Inner join – default join is Inner join.

2.Outer join

a)Right Outer join or Right join

b)Left Outer join or Left join

c)Full Outer join

3. Cross join

--inner join

select c.c_id,c.c_name,c.language_known,o.orderno,o.product_name from cts.Customer c inner join

cts.orderid o on c.c_id=o.c_id

--left outer join

select c.c_id,c.c_name,c.c_address,o.product_name from cts.Customer c left outer join cts.orderid o on

c.c_id=o.c_id

--inner join using and clause

select c.c_id,c.c_name,o.product_name from cts.Customer c join cts.orderid o on c.c_id=o.c_id and

c.c_address='Andhrapradesh'

--alternate way for inner join using where clause

select c.c_id,c.c_name,o.product_name from cts.Customer c join cts.orderid o on c.c_id=o.c_id where

c.c_address='Andhrapradesh'

--to find who didnt bought product

select o.c_id,o.product_name from cts.Customer c right join cts.orderid o on c.c_id=o.c_id where c.c_id

is null

Aggregate Functions:

Aggregate functions perform a calculation on a set of values and return a single value. Except for COUNT, aggregate functions ignore null values. Aggregate functions are frequently used with the GROUP BY clause of the SELECT statement.

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Some of the Aggregate Functions are:

a)count() b)avg()

c)sum() d)max()

e)min()

Examples:

AVG() - Average value of columns

SELECT AVG(Salary) FROM CUSTOMERS

Value = 4675

COUNT() - number of rows

Select COUNT(*) FROM CUSTOMERS

Value = 4

SELECT COUNT (DISTINCT Salary) FROM CUSTOMERS

Value = 3

MAX() - Maximun or Highest number in a column

SELECT MAX(Salary) FROM CUSTOMERS

Value = 5000

MIN() - Minimum or Lowest number in a column

SELECT MIN(Salary) FROM CUSTOMERS

Value = 4000

SUM() - Total number in a column

SELECT SUM(Salary) FROM CUSTOMERS

Value = 18500

--to find distinct no. of customers

select distinct COUNT(c.c_id) "No. of customers" from cts.Customer c join cts.orderid o on c.c_id=o.c_id

--Alternatively, the above statement can be written as

select distinct COUNT(c_id) "No. of distinct customers" from cts.orderid

-- sum function

select SUM(Order_price) from cts.orderid where Order_Price>76

select c_id,SUM(Order_Price),product_name "total amount" from cts.orderid group by

c_id,product_name

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select c_id,SUM(Order_Price) from cts.orderid group by c_id having c_id > 1002

select c_id,SUM(Order_Price) "Total price" from cts.orderid where c_id > 3 and Order_Price >100 group

by c_id having SUM(Order_Price) > 10

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4.VIEWS

Points to remember:

In SQL, a view is a virtual table based on the result-set of an SQL statement.

A view contains rows and columns, just like a real table. The fields in a view are fields from one

or more real tables in the database.

You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the

data were coming from one single table.

Creating a view:

Syntax:

CREATE VIEW view_name AS

SELECT column_name(s)

FROM table_name

WHERE condition

Updating a view:

Syntax:

ALTER VIEW view_name AS

SELECT column_name(s)

FROM table_name

WHERE condition

Dropping a view:

Syntax:

DROP VIEW view_name

--Example 1: Create a view that displays all the entries of employee table.Also display the view

create view employee as select * from cts.employee select * from employee

--Example2: create a view employee with attributes id, name where salary=55000 from employee

table. Also display the view.

create view employeeIDandName (id,name)as select id,name from cts.employee where salary=55000;

select * from employeeIDandName

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--Example 3: create a view emp with name and with the condition that all salary reduced by half from

employee table.

create view employeeHalfSalary (name,salary) As select name,salary/2 from cts.employee; select * from employeeHalfSalary;

--Example 4: Create a view that has all the details about the customer whose address is “chennai”

create view Viewcustomers as select * from customers where addres='Chennai' select * from Viewcustomers

--Example 5: Alter the above view and make the salary to be twice the actual salary in employee table.

alter view doubleEmpSalary(name,salary)as(select name,2*salary from cts.employee); select * from doubleEmpSalary;

--Example 6: drop the view created.

drop view employee;

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5.CONTROL FLOW CONSTRUCTS IN SQL

--***** using if statement

if ((select id from cts.employee where name = 'lena prasanna') = 346238)

begin

print 'Andhrapradesh'

end

else

begin

print 'Tamilnadu'

end

--**** using while loop

--Prints 5 tables till 100

declare @count int

declare @num int

--Note: every variables declared, should be initialized to any number

set @num = 0

set @count = 1

while @num < 100

begin

set @num = 5 * @count

print @num

set @count = @count + 1

end

--*****using if exists statement

if exists (select name from cts.employee where name='lena prasanna')

print 'Andhrapradesh'

else

print 'Tamilnadu'

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--*****using switch case

--tax calculation

--NOTE: using syntax 1, we can’t evaluate an expression. Below is the example of using syntax 1.

1.simple case expression function

select name,States=case name

when 'harsha' then 'Andhrapradesh'

when 'sivasaiprasad' then 'Andhrapradesh'

when 'lena prasanna' then 'Andhrapradesh'

when 'kishore' then 'Tamilnadu'

when 'chanakya' then 'Andhrapradesh'

else 'karnataka'

end from cts.employee

--METTL syntax if we use syntax 1

select name,case name

when 'harsha' then 'Andhrapradesh'

when 'sivasaiprasad' then 'Andhrapradesh'

when 'lena prasanna' then 'Andhrapradesh'

when 'kishore' then 'Tamilnadu'

when 'chanakya' then 'Andhrapradesh'

else 'karnataka'

end "States" from cts.employee

--using syntax 2 , we can evaluate expression (search case expression function which evaluate result

based on Boolean expression)

select name, Tax_amount =case

when SALARY >40000 then '20000'

when SALARY <=40000 and SALARY <=30000 then '10000'

else '7500'

end

from cts.employee

--METTL syntax if we use syntax 2

select name, case

when SALARY >40000 then '20000'

when SALARY <=40000 and SALARY <=30000 then '10000'

else '7500'

end

“Tax_amount” from cts.employee

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6.USING LOCAL VARIABLES use dn016_346238

--find odd or even

declare @num int;

set @num=6;

if (@num % 2 = 0)

print 'Number is even';

else

print 'Number is odd';

--calculate tax using basic pay

declare @basicPay money;

declare @tax money;

set @basicPay=600000;

if (@basicPay > 500000)

set @tax= @basicPay * 20 /100;

else if (@basicPay >300000)

set @tax= @basicPay * 10 / 100;

else if (@basicPay >200000)

set @tax = @basicPay * 5/100;

else

set @tax = 0;

print ' The tax amount for the given '+cast(@basicPay as nvarchar(50))+ ' is ' +

convert(nvarchar(50),@tax);

--selecting employee details whose ID is greater than 500 using local variables

use dn016_346238

declare @id int;

set @id=500;

select * from cts.Employee where EmpID > @id;

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7.CURSORS

Note:

attributes with "Identity property" cannot be changed normally. This applies to cursors also.

Syntax for declaring cursors:

declare cursor_name cursor

for

<--TSQL Statements-->

[For update (of column_name)]

note: the contents within [] and () are optional.

Steps involved in cursors:

We need to follow 5 steps on dealing with cursors:

1.Declare Cursor

2.Open Cursor

3.Fetch from cursor

4.Close Cursor

5.Deallocate Cursor

we have 6 priority levels

1.FIRST

2.LAST

3.NEXT

4.PRIOR

5.ABSOLUTE

6.RELATIVE

Declaring cursors as a local variable

DECLARE @varcursor CURSOR

SET @varcursor = CURSOR FOR


OPEN @varcursor

FETCH @varcursor

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WHILE( @@FETCH_STATUS = 0)

BEGIN

FETCH @varcursor

END

CLOSE @varcursor

DEALLOCATE @varcursor

--TYPE 1: FORWARD ONLY CURSOR

--NOTE:Updation made using cursor, affects the cursor as well as in the main table.

-- we cannot use the priority levels like FIRST,LAST,PRIOR,ABSOLUTE,RELATIVE. We can use only NEXT

prioriy level in this type.

--Step 1: Declaring cursor

declare myCursor cursor --myCursor is the cursor name.It is not a variable. By default, any cursor is a

Forward-only cursor

for


--Step 2: Opening cursor

--Cursor will be created only when step 2 is executed

Open myCursor

--Step 3: Fetch records using my cursor

FETCH next FROM myCursor

--NOTE: we can use "NEXT" only. We cannot use other

--Intermediate step: update records

update cts.employee set name= 'Lenaprasanna',address ='Andhrapradesh' where current of myCursor

--Normal update query

update cts.employee set name= 'Sriharsha',address ='Hyderabad' where id=346538

--Step 4: Closing cursor

close myCursor

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--Step 5: Cursor De allocation

deallocate myCursor

Forward Only Scroll :

-- we can use all the keywords like FIRST,LAST,NEXT,PRIOR,ABSOLUTE,RELATIVE.

Declaration of Forward only Scroll:

declare myCursor cursor scroll

for


open myCursor

--NOTE: All the priority levels like FIRST,LAST,NEXT,PRIOR,ABSOLUTE,RELATIVE are available in the

forward only scroll type cursor

FETCH first FROM myCursor --retrieves first record

FETCH last FROM myCursor--retrieves last record

FETCH next FROM myCursor --retrieves next available record

FETCH prior FROM myCursor -- moves one step back

--ABSOLUTE - Moves to absolute position we specify

FETCH absolute -2 FROM myCursor --it moves 2 entries before.

FETCH absolute 3 FROM myCursor --it will move 2 steps ahead.

FETCH relative 3 FROM myCursor --moves to the specified 3rd position from the current position

--Updating records using cursor

update cts.employee set name= 'Sivaprasad',address ='hyderabad' where current of myCursor

--Displaying the updated table


--USING FORWARD ONLY CURSOR: To add a constraint that a particular column alone to be updated,

we can redefine the declaration by including “for update” keyword followed by the column names

which we need to modify.

--Step 1:

declare myCursor cursor

for

select * from cts.employee --IT IS MANDATORY.. Since cursor is like pointer, it should be

allowed to point to a particular table. Here it points to cts.employee table

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for update of name,address --This field is optional. Now,Updating any fields other than name and

address is not valid with this cursor.

--Step 2:

open myCursor

--Step 3:

update cts.employee set name= 'SriHarshaChilla',address ='Andhrapradesh' where current of myCursor

--Step 4 and Step 5:

close myCursor

deallocate myCursor

--TYPE2: DYNAMIC CURSOR

--NOTE:Changes made using dynamic cursor, affects the main table as well as the table created by the

cursor in tempdb.

--Hence, Dynamic cursors are called as "SENSITIVE CURSORS"

--Step1: Cursor Declaration:

declare myCursor cursor dynamic

for


--Step2: Opening cursor

open myCursor

--Step 3: fetching using cursor

--Note:Except ABSOLUTE, the others like NEXT,PRIOR,FIRST,LAST,DYNAMIC can be used

FETCH next from myCursor

FETCH first FROM myCursor

FETCH last FROM myCursor


FETCH prior FROM myCursor

FETCH relative 3 FROM myCursor

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--updating entries using Dynamic Cursor

update cts.employee set name='Lenaprasanna' where current of myCursor

update cts.employee set id=346200 where name = 'S.Kishore'

--Step 4: Closing and freeing the resource

close myCursor

deallocate myCursor

--TYPE 3: STATIC CURSOR

--NOTE: Changes made in the main table doesnot affect the cursor. Because this cursor retrieves the data

from tempdb which initializes datas from the table when the cursor is created and it never checks the

current updated main table again even if the changes are made. Note that, this cursor is READ ONLY.

--Hence, Static cursors are called as "INSENSITIVE CURSORS AND NOT UPDATABLE".

--FOR UPDATE is not valid for static cursors. SO dont give for update keyword in the cursor declaration.

--All the priority levels can be used.

--Step1: Cursor Declaration

declare myCursor cursor static

for



open myCursor


-- All priority levels like ABSOLUTE,NEXT,PRIOR,FIRST,LAST,DYNAMIC can be used.






FETCH absolute -2 FROM myCursor

FETCH absolute 3 FROM myCursor


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--updating entries using static Cursor

update cts.employee set name='Lenaprasanna' where current of myCursor --this statement is INVALID

as the cursor is READONLY. No update can be done with this cursor.

--Step4: Closing and deallocating the cursor

close myCursor

deallocate myCursor

--TYPE4: KEYSET DRIVEN CURSORS

--Note: This cursors are used to update any key columns

--Here, When we update any entry using cursor, unlike Dynamic cursor, this cursor will make the current

pointing entry to be null and make the updated entry in the end of the base table.

--If we update using normal update query, the corresponding values pointed by the cursor becomes null

and no actual entry will be added in the end of the table.

--Step1: Cursor Declaration

declare myCursor cursor keyset

for



open myCursor


-- All priority levels like ABSOLUTE,NEXT,PRIOR,FIRST,LAST,DYNAMIC can be used.






FETCH absolute -2 FROM myCursor

FETCH absolute 3 FROM myCursor


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--updating entries using keyset Cursor

update cts.employee set id=346534 where current of myCursor

--Step 4: Closing and freeing the resource

close myCursor

deallocate myCursor

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8.CREATING USER DEFINED DATATYPES

create type udtDescription from nvarchar(max);

create table cts.UserDescription

(

UserName udtDescription,

Passwd nvarchar(50)

);

insert into cts.UserDescription values ('Lenaprasanna','12345678');

insert into cts.UserDescription values ('kishore','32445568');

select * from cts.UserDescription;

9. STORED PROCEDURES Note:

There are three types of stored procedures. Namely,

o System Stored procedures

o User defined Stored procedures

o Extended Stored procedures

System Stored Procedures

Many administrative activities in SQL Server are performed through a special kind of

procedure known as a system stored procedure. For example, sys.sp_changedbowner is

a system stored procedure. System stored procedures are physically stored in the

Resource database and have the sp_ prefix. System stored procedures logically appear in

the sys schema of every system- and user-defined database. In SQL Server 2008, GRANT,

DENY, and REVOKE permissions can be applied to system stored procedures.

Some of the system Stored Procedures are sp_rename, sp_execute, etc.

Example:

o Changing the name of the column in the table using sp_rename stored

procedure:

EXEC sp_rename

‘dbo.Orders.Details’, -- Fully Qualified column name

‘OrderDetails’, -- New column name

‘COLUMN’ -- Object Type

http://technet.microsoft.com/en-us/library/ms190940(v=sql.105).aspx

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o Changing the name of the table using sp_rename stored procedure:

EXEC sp_rename

‘dbo.Orders’, -- Existing Table including Schema Name

‘OrderDetails’, -- New column name

‘OBJECT’ -- Object Type

o Changing the index of the table using sp_rename stored procedure:

EXEC sp_rename

'dbo.Orders.PK__Orders__C3905BAF6A30C649', -- Existing Table

including Schema Name

'IDX_PK_C_OrderID', -- Fully Qualified index name

‘INDEX’ -- Object Type

Note: Procedure can be executed using EXEC command followed by the procedure name and the arguments(optional)

User Defined Stored Procedures

--**Simple procedure without arguments

--Displays customer details

create procedure procCustomerList

As

Begin

select id,address from cts.employee

select empid,dob from cts.employees

end

--Procedure call

exec procCustomerList

--**Simple procedure with arguement

--Displays customer details for the given id

create procedure procCustomerList @id int,@empname varchar(30)

As

Begin

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select id,address from cts.employee where id=@id

select empid,dob from cts.employees where empname=@empname

end

--procedure call

exec procCustomerList 346238,'lenaprasanna'

--Procedure to find fibonacci of n numbers without recursion

create procedure fibonacci @num int

as

begin

declare @fib1 int,@fib2 int,@fib int,@temp int

set @fib1 = 0

set @fib2 = 1

set @temp = 2

print @fib1

print @fib2

while(@temp < @num)

begin

set @fib=@fib1+@fib2

print @fib

set @fib1=@fib2

set @fib2=@fib

set @temp = @temp + 1

end

end

--Function call

exec fibonacci 5

--*** nested procedures

--procedure to find fibonacci with recursion

alter procedure recursiveFibonacci @fib1 bigint, @fib2 bigint,@num bigint

as

begin

if @num = 0

return

begin

if @fib1 = 0

print 0

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declare @temp bigint

set @temp = @fib1 + @fib2

if @num <> 1

print @temp

set @num = @num - 1

exec recursiveFibonacci @fib2,@temp,@num

end

end

--Function call

exec recursiveFibonacci 0,1,10

--If a procedure contains an output variable, use the steps given in the comments:

--declare @var int

--exec recursiveFibonacci 0,1,8,@var output

--print @var

-- HANDS ON Exercises:

--Question 1: Procedure to insert entries when CustId and CompName is not NULL. Else display

respective error message

create procedure procCustIDCompNameVerify @custID int,@compName varchar(30),@contName

varchar(30),@contTitle varchar(30),@address varbinary(max),@city varchar(30),@region

varchar(30),@postalcode int,@country varchar(30),@phone bigint, @fax varchar(30),@NoOfOrder int

as

begin

declare @tempCustId varchar(30)

set @tempCustId = cast(@custID as varchar(30))

if @tempCustId is not NULL and @compName is not NULL

begin

insert into Sales.Customers

values(@tempcustID,@compName,@contName,@contTitle,@address,@city,@region,@postalcode,@c

ountry,@phone,@fax,@nooforder)

end

if @tempcustId is NULL

begin

print 'ALERT:Cant insert. Customer ID is null'

end

if @compName is NULL

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begin

print 'ALERT:Cant insert. Company name is null'

end

end

--Function call

exec procCustIDCompNameVerify

1,'cognizant','Lenaprasanna','ProgrammerAnalystTrainee',NULL,'Tenali','Andhrapradesh',531402,'India',

8144386636,'044-4120221',5

select * from Sales.Customers

--Question 2: procedure that takes two parameters namely type and pattern as input and display first

name or last name based upon the type provided as input.

create procedure procPatternMatch @type nvarchar(30),@pattern nvarchar(30)

as

begin

if( @type = 'FirstName' )

begin

select * from HumanResource.Employees where FirstName like @pattern

end

else if (@type = 'LastName')

begin

select * from HumanResource.Employees where LastName like @pattern

end

end

--Procedure call

exec procPatternMatch 'FirstName','k%'

exec procPatternMatch 'LastName','_a_e_n'

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10.FUNCTIONS

--Type 1: scalar valued function

--case 1:create a function without arguments

--This function prints 124 always

create function display()

returns int

as

begin

declare @num int

set @num=124

return @num

end

--function call

select dbo.display()

--or

print dbo.display()

--function call with alias name

select dbo.display() "My value"

--droping a function

drop function dbo.display

--case 2:create a function with single argument

-- this function concatenates '0' with the id passed to it

create function getdetails(@cust int)

returns nvarchar(20)

as

begin

return '0'+cast(@cust as nvarchar(20))

end

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--function call

--a) direct call

print dbo.getdetails(678)

--b) call from table entry without alias name

select name,id,dbo.getdetails(id) from cts.employee

--c) call from table entry without alias name

select name,id,dbo.getdetails(id) "Call from function" from cts.employee

--case 3:create a function with two arguments

-- this function concatenates the employee name with the id passed to it

create function appendName(@id as int,@cus_name as varchar(50))


as

begin

return @cus_name +convert(nvarchar(30),@id)

end

--function call

a) with default arguments

select dbo.appendName(123,'lena')

b) for all table entries without alias name

select name,id,dbo.appendName(id,name) from cts.employee

c) for all table entries with alias name

select name,id,dbo.appendName(id,name) "Appended Name" from cts.employee

--***Exercise 1

--calculate tax with salary from table

create function calculate_tax(@sal as money)

returns money

as

begin

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declare @tax money

set @tax=0

if @sal >50000

begin

set @tax=@sal *20/100 --20% tax of the salary

end

else if @sal >40000

begin


end

else if @sal >30000

begin


end

else

begin

set @tax=0 --no tax if sal <=30000

end

return @tax

end

--function call

select name,SALARY,dbo.calculate_tax(SALARY) "Estimated Tax Amount" from cts.employee

--***Altering a function

alter function calculate_tax(@sal decimal(8,2))


as

begin

declare @tax decimal(8,2)

set @tax=0

if @sal >50000

begin


end

else if @sal >40000

begin


end

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else if @sal >30000

begin


end

else

begin

set @tax=0 --no tax if sal <=30000

end

return cast(@tax as nvarchar(20))

end

--function call

select name,SALARY,dbo.calculate_tax(SALARY) "Estimated Tax Amount" from cts.employee

--Type 2:inline table valued function

--case1:without arguments

--displays id,name and address of all employees in the table

create function getEntryOfEmployee()

returns table

as

return

(

select id,name,address from cts.employee where salary > 45000

)

--case2:with arguments

create function getEntryOfEmployeeWithArg(@salCondition as money)

returns table

as

return

(

select id,name,address from cts.employee where salary > @salCondition

)

--function call

select * from dbo.getEntryOfEmployee()

select * from dbo.getEntryOfEmployeeWithArg(346238)

select * from dbo.getEntryOfEmployeeWithArg(55000)

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--Type 3:multi statement table valued function

alter function addOrDisplayEntries(@ID int)

returns @employeelist table

(id int,name varchar(50),salary money)

as

begin

if @ID is NULL

begin

insert @employeelist

select id, name, salary from cts.employee

end

else

begin

insert into @employeelist

select id, name, salary from cts.employee where id = @ID

end

return

end

--function call

select * from dbo.addOrDisplayEntries(3455)

select * from dbo.addOrDisplayEntries (346238)

--(or)

--call using a local variable

declare @id int

set @id=346238

select * from dbo.addOrDisplayEntries (@id)

--dropping a function

drop function calculate_tax

Note: While dropping a function, no need to include paranthesis () at the end of the function name.

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--Hands on exercises

--Question 1: Function that returns the number of orders placed by the customer

--function definition

create function NumberOfOrders(@cusId int)


as

begin

declare @order int

--From the table, get the count of the no. of orders placed by the customer

select @order=count(orderno) from cts.orderid where c_id=@cusId

return convert( nvarchar(20),@order) -- provides the no. of orders placed by the customer

end

--function call

print dbo.NumberOfOrders(1000) "No. Of Orders"

--Question 2: Function that takes ‘LongName’ or ‘ShortName’ as input and prints LastName of the

employee if ‘ShortName’ is passed as an argument. Else this function wil return the FirstName along

with his LastName


create function displayNames (@name nvarchar(9))

returns @EmpTable table(ID int,Name nvarchar(50))

as

begin

if (@name = 'ShortName')

begin

-- Initialize @EmpTable with LastName

insert @EmpTable select empid, LastName from cts.employees

end

else if (@name = 'LongName')

begin

-- Initialize @EmpTable FirstName LastName

insert @EmpTable select empid, (FirstName + ' ' + LastName) from cts.employees

end

-- Provides the value of @EmpTable as the result

return

end

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--function call

select * from dbo.displayNames('ShortName')

select * from dbo.displayNames('LongName')

--Question 3: Functions that takes region as input and prints all the users in the particular region


create function displayOthers(@region as nvarchar(50))

returns table

as

return

(

--Select all the users who all are currently in the given region

select name from cts.employee where address = @region

)

--function call

select * from displayOthers('Hyderabad')

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11.EXCEPTION HANDLING IN STORED PROCEDURE

--**factorial example

--case 1: Factorial using procedure - with Input parameter,without Output parameter

create procedure procFactorial @num int

as

begin try

declare @count int,@result int

set @count = 1

set @result = 1

while @count <= @num

begin

set @result = @result * @count


end

select @result "Factorial value"

end try

begin catch

select ERROR_NUMBER(),ERROR_MESSAGE()

end catch

--procedure call

exec procFactorial 5

--case 2: Factorial using procedure - with Input and Output parameter

alter procedure procFactWithOutputParameter

@num int,@result numeric(38,0) output

as

begin try

declare @count int

set @result = 1

set @count = 1

--if incase we provide 0 as input, It should obviously return 1 SINCE 0! = 1


begin

set @result = @result * cast(@count as numeric(38,0))

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end

end try

begin catch

select ERROR_NUMBER() "ERROR NUMBER",ERROR_MESSAGE()"ERROR MESSAGE"

end catch

--procedure call

declare @inputvar int,@outputvar numeric(38,0)

set @inputvar = 30

set @outputvar = 1

exec procFactWithOutputParameter @inputvar,@outputvar output

select @inputvar "Input value",@outputvar "Factorial value"

--or

print cast(@inputvar as varchar(4)) + '!=' + cast(@outputvar as varchar(4))

--case 3:Function to find factorial - without recursion

alter function funcFactorial (@num int)

returns numeric(38,0)

--Note:Reason for using numeric(38,0) because if we enter any value more than 13! using int type, it

wil show arithmetic overflow error

as

begin

declare @count int

declare @result numeric(38,0)

set @count = 1

set @result = 1 --if incase we provide 0 as input, It should obviously return 1


begin

set @result = @result * cast(@count as numeric(38,0)) --multiplication between int and

numeric type. so typecast int to numeric as the result is of type numeric.


end

return @result

end

--Function call

select dbo.funcFactorial(30) "Factorial value"

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--case 4:Function to find factorial - with recursion

alter function funcRecursiveFact(@num numeric(38,0))

returns numeric(38,0)

as

begin

declare @prod numeric(38,0)

if @num<=1

return 1

else

set @prod = cast(@num as numeric(38,0)) * dbo.funcRecursiveFact(@num-1)

return @prod

end

--Function value

select dbo.funcRecursiveFact(30) "Factorial value"

--case 5: Creating a procedure in another procedure

create procedure procInProcFactorial @inputval int, @result numeric(38,0) output

as

begin

declare @init int

set @init = 1

exec procFactWithOutputParameter @inputval,@result output

return @result

end

declare @var int

exec procInProcFactorial 5,@var output

select @var "Factorial value"

--case 6: Creating a procedure in another procedure

create procedure procfactorialwithoutput @num int,@result numeric(38,0) output

as

begin try

declare @prod numeric(38,0)

set @prod=1

while(@num >1)

begin

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set @prod=@prod * @num

set @num=@num - 1

end

set @result=@prod

end try

begin catch

select ERROR_NUMBER(),ERROR_MESSAGE()

end catch

--second procedure

alter proc procinprocfact

@max int,

@result numeric(38,0) output

as

begin

declare @init int

set @init=0

while(@init<= @max)

begin

exec procfactorialwithoutput @init,@result output

print cast(@init as varchar(20))+'!='+cast(@result as varchar(max))

set @init = @init + 1

end

end

--Function call

declare @var numeric(38,0)

exec procinprocfact 30,@var output

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12.TRIGGERS

--Type 1:DML triggers

--a)AFTER TRIGGER:

--Concept: When some one tries to modify the entries of the table once the trigger is created,The newly --

entered entry will be reflected in the basetable.

--Incase the data is inserted, "Inserted table" will hold the newly inserted value, Incase the data is

deleted, the old values that is currently being deleted will be moved to "Deleted table" and the same will

be removed from the basetable , Incase the data is updated,the newly entered value is updated into the

basetable and the old value will be stored in the magic table called "Deleted" and the new value is stored

in the another magic table called "Inserted"

-- We can use any of the entries in these 2 magic tables and we insert in the Auditing table.

--To drop the table named "AuditingTable", if exists prior to create it.

if object_id ('AuditingTable' ,'u') is not null

drop table AuditingTable

create table AuditingTable

(

EmpID int,

Trigger_msg nvarchar(max),

Modified_date date

--if u want to print date and time, use the datatype "datetime"

)

--To drop the existing trigger

if OBJECT_ID('EmployeeTrigger','TR') is not null

drop trigger EmployeeTrigger

--Example 1: Creating trigger to an existing table called cts.employee

create trigger EmployeeTrigger

on cts.employee

after insert

as

begin

declare @id int

--"Inserted" table is a magical table

select @id=i.id from inserted i

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--if u want to insert date and time together, use "sysdatetime()"

insert into AuditingTable (EmpID,Trigger_Msg,Modified_date)

values (@id,'New record inserted to cts.employee table',getDate())

end

--Trigger is called automatically when the data is inserted

insert into cts.employee

values(4557,'Lenaprasanna','Andhrapradesh','[email protected]',9876544334,25000)

--To view the inserted data

select * from AuditingTable

--Example 2: create a single trigger that responds to update and delete

create trigger employeeUpdateDeleteTrigger

on cts.employee

after update,delete

as

begin

declare @id int




values (@id,'A record is modified in cts.employee table',getDate())

end

--To call the trigger automatically when the below 2 statements are executed

delete from cts.employee where id=4557

update cts.employee set name='chanakya' where id=346234

--To view the deleted and updated data


--Example 3:create a single trigger that responds to insert, update and delete

create trigger employeeInsUpdDelTrigger

on cts.employee

after insert,update,delete

as

begin

declare @id int



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--"deleted" table is an another magical table

select @id=i.id from deleted i


values (@id,'Insert,Delete or update action is perfomed in the table',getDate())

end

--To call the trigger automatically when any of the below 3 statements are executed alone or in

combinations

insert into cts.employee

values(4557,'Lenaprasanna','Andhrapradesh','[email protected]',9876544334,25000)

delete from cts.employee where id=4557

update cts.employee set name='chanakya' where id=346234

--NOTE 1:

--Updating a row happens in two ways: First it will delete the corresponding entry from the basetable

and put it into the "deleted" table(magic table) [Which means, deleted table will hold the old values] and

second, the provided new entry is entered into the base table again, which will be reflected in the

"inserted" magic table[which means, the "inserted table" will hold only the new values].

--The order at which the inserted and deleted tables are called in the trigger has an influence over the

Auditing table.

--In the above example, we used the value of id from "inserted" table and passed the result on to a local

variable called @id

-- and in the next statement, we have over written the value of id from "deleted" table. which means,

now, the variable @id will hold the old value.

--If this order of these 2 statements are interchanged, the @id value will hold the new value

--NOTE 2: If we use the entry of "deleted table" for the trigger that is called by an insert action, it will

return NULL.

--To view the Auditing table data


--To view the base table data


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--b)INSTEAD OF TRIGGER

--Concept: When some one tries to modify the entries of the table once the trigger is created, The newly

entered entries will not be reflected in the basetable but instead the two magical tables called "inserted"

and "deleted" will hold the values as discussed in the AFTER TRIGGER.

--NOTE: Instead of trigger will have HIGH PRIORITY than AFTER trigger

--Example 1:

create trigger InsteadOfemployeeInsUpdDelTrigger

on cts.employees

Instead Of insert,update,delete

as

begin

declare @id int

--"Inserted" table is a magical table/

select @id=i.empid from inserted i

--"deleted" table is an another magical table/

select @id=i.empid from deleted i


values (@id,'Alert: some body tried to Modify it',getDate())

end

--calling InsteadOf trigger

update cts.employees set empname='Lenaprasanna' where empid=346238

--To view the Auditing table data


--To view the basetable data


--***********Syntax for Disabling / Enabling triggers:

--Case 1: DDL triggers

disable trigger DDL_Trigger_Name on database

enable trigger DDL_Trigger_Name on database

--case 2:DML triggers

alter table tablename disable trigger DML_trigger_Name

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--*****TRIGGERS HANDS ON****

--creating table consists of modified records

create table auditing

(

id int,

trigger_msg nvarchar(max),

mod_date datetime

)

--question 1:

create trigger preventDeleteMoreThanOnceTrigger on Sales.OrderDetails

instead of delete

as

begin

declare @count int

declare @id int

select @count=count(*) from deleted

print @count

if @count<=1

begin

select @id=i.OrderID from deleted i

delete from Sales.OrderDetails where OrderID=@id

end

else

print 'Alert: You attempted to delete more than one record at a time!!!!'

end

--calling trigger

delete from Sales.OrderDetails where productID=21

--Question 2:

create trigger preventModifyTrigger

on sales.customers

instead of update

as

begin

declare @id int;

declare @comp varchar(30);

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select @id=i.CustomerId from inserted i;

select @comp=i.CompanyName from inserted i;

if update(CustomerId) --checks only the inserted table alone. It won’t checks the basetable

insert into auditing values(@id,'The user is attempting to modify

customerId',getdate())

else

update Sales.Customers set CompanyName=@comp where CustomerId=@id

end

--calling trigger

update sales.customers set CompanyName='CTS' where customerid=61

update sales.customers set Customerid=61 where companyName='CTS'

select * from sales.customers

select * from auditing

Type 2:DDL TRIGGERS

--Table structure

create table ObjectTracking

(

TrackingID bigint identity(1,1),

TrackingDate datetime NOT NULL default getdate(),

DatabaseName varchar(500),

EventType varchar(500),

ObjectName varchar(500),

ObjectType varchar(500),

LoginName varchar(500),

HostName varchar(500),

SqlCommand nvarchar(max),

ModifiedDateTime datetime

)

--DDL trigger Creation

create trigger databaseTrigger

on database

for CREATE_PROCEDURE,CREATE_TABLE

--Note: DDL_DATABASE_LEVEL_EVENTS - Defines all the DDL database events on

CREATE_PROCEDURE,CREATE_TABLE,ALTER_PROCEDURE,DROP_PROCEDURE,ALTER_TABLE,

DROP_TABLE,CREATE_FUNCTION,ALTER_FUNCTION,DROP_FUNCTION,CREATE_VIEW,ALTER_VIEW,

DROP_VIEW,CREATE_INDEX,ALTER_INDEX,DROP_INDEX

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as

begin

declare @data XML

declare @HostName varchar(500)

set @data = EVENTDATA()

--assigning EVENTDATA() to a local variable @data.

--Note: After the above assignment, calling EVENTDATA().value and @data.value will be same

hereafter

set @HostName = HOST_NAME()

--HOST_NAME() retrieves the machine name. In this step, we are assigning HOST_NAME() to a

local variable @HostName

insert into ObjectTracking

(

DatabaseName,

EventType,

ObjectName,

ObjectType,

LoginName,

HostName,

SqlCommand,

ModifiedDateTime

)

values(

@data.value('(/EVENT_INSTANCE/DatabaseName)[1]','varchar(500)'), --The first parameter in

the @data.value has the entire path where the datas are available.[1] in the first parameter retrieves

the current record. It returns in the XML format. The second parameter converts the XML type

parameter to varchar(500)

@data.value('(/EVENT_INSTANCE/EventType)[1]','varchar(500)'),

@data.value('(/EVENT_INSTANCE/ObjectName)[1]','varchar(500)'),

@data.value('(/EVENT_INSTANCE/ObjectType)[1]','varchar(500)'),

@data.value('(/EVENT_INSTANCE/LoginName)[1]','varchar(500)'),

@HostName,

@data.value('(/EVENT_INSTANCE/TSQLCommand)[1]','varchar(500)'),

sysdatetime()

)

end

--calling the trigger.

--The above trigger will be called when we create a new procedure or table and stores all the details in

the ObjectTracking table.

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--creating a new table to check the newly created trigger

create table TriggerCheck

(

id int,

name varchar(50)

)

--displaying the ObjectTracking table entried

select * from ObjectTracking

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13.INDEXING IN SQL

--Note: This is the program given by our trainer Mr. Santhosh. This includes both the commands and

its results

use santhosh_dn016

go

CREATE TABLE employeeDetails(

id INTEGER NOT NULL PRIMARY KEY,

first_name VARCHAR(10),

last_name VARCHAR(10),

salary DECIMAL(10,2),

startDate DATETIME,

region VARCHAR(10),

city VARCHAR(20),

managerid INTEGER

);

GO

INSERT INTO employeeDetails VALUES (1, 'Jason' , 'Martin', 5890,'2005-03-22','North','Vancouver',3);

GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (2, 'Alison', 'Mathews',4789,'2003-07-21','South','Utown',4);

GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (3, 'James' , 'Smith', 6678,'2001-12-01','North','Paris',5);

GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (4, 'Celia' , 'Rice', 5567,'2006-03-03','South','London',6);

GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (5, 'Robert', 'Black', 4467,'2004-07-02','East','Newton',7);

GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (6, 'Linda' , 'Green' , 6456,'2002-05-19','East','Calgary',8);

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GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (7, 'David' , 'Larry', 5345,'2008-03-18','West','New York',9);

GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (8, 'James' , 'Cat', 4234,'2007-07-17','West','Regina',9);

GO

--(1 rows affected)

INSERT INTO employeeDetails VALUES (9, 'Joan' , 'Act', 6123,'2001-04-16','North','Toronto',10);

GO

--(1 rows affected)

select * from employeeDetails;

GO

--id first_name last_name salary start_Date region city managerid

----------- ---------- ---------- ------------ ----------------------- ---------- -------------------- -----------

-- 1 Jason Martin 5890.00 2005-03-22 00:00:00.000 North Vancouver 3

-- 2 Alison Mathews 4789.00 2003-07-21 00:00:00.000 South Utown 4

-- 3 James Smith 6678.00 2001-12-01 00:00:00.000 North Paris 5

-- 4 Celia Rice 5567.00 2006-03-03 00:00:00.000 South London 6

-- 5 Robert Black 4467.00 2004-07-02 00:00:00.000 East Newton 7

-- 6 Linda Green 6456.00 2002-05-19 00:00:00.000 East Calgary 8

-- 7 David Larry 5345.00 2008-03-18 00:00:00.000 West New York 9

-- 8 James Cat 4234.00 2007-07-17 00:00:00.000 West Regina 9

-- 9 Joan Act 6123.00 2001-04-16 00:00:00.000 North Toronto 10

--(9 rows affected)

CREATE INDEX i_empno ON employeeDetails(id);

CREATE NONCLUSTERED INDEX NI_ID_FirstName ON employeeDetails(ID, First_Name)

GO

CREATE NONCLUSTERED INDEX NCI_FirstName ON employeeDetails(First_name ASC)

GO

CREATE NONCLUSTERED INDEX NCI_FirstName ON employeeDetails(First_name ASC) WITH

(DROP_EXISTING = ON)

GO

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CREATE NONCLUSTERED INDEX NCI_FirstName ON employeeDetails(ID, First_name DESC) WITH

(DROP_EXISTING = ON)

GO

DROP INDEX employeeDetails.i_empno

-- The next statement is equivalent to the previous one

--DROP INDEX i_empno ON employee

drop table employeeDetails;

GO

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14.TRANSACTION AND LOCKING

Notes to Remember:

Transaction is a unit of work in the database

Transaction commits the statements if there is no error in statements and becomes the

permanent part of database

Transaction is rolled back if there are errors in statements and all the data modifications are

discarded.

Types of transaction:

a)Auto Commit:

Each and every process is a transaction in SQL server.

b)Explicit:

A transaction is explicitly started with 'BEGIN TRANSACTION' and ended with 'COMMIT'

or 'ROLLBACK'

c)Implicit:

A transaction implicitly started and explicitly ended with ‘commit’ or ‘rollback’

--In general, all the queries we have tried before like INSERT,UPDATE,DELETE are of type "AUTO

COMMIT TRANSACTION"

--Note: @@trancount => Initially it will have the value 0.It is automatically incremented by 1 if it

sees BEGIN TRANSACTION KEYWORD and decremented by 1 if it sees commit or rollback

Example for explicit transaction :

--Note: Using ‘GO’ is one of the code standard and it is not mandatory always.

begin transaction InsertTransaction

GO

Insert into cts.employee values

(346530,'saisivaprasad','Hyderabad','[email protected]',9865778345,55000)

commit transaction

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Example for rollback:

begin transaction InsTransRoll

Insert into cts.employee values

(346530,'Karthikeyan','Chennai','[email protected]',9865765545,55000)

--since the ID is a primary key and it is already present in the table, it will not insert the

above mentioned value.

--If we include this between begin transaction and rollback transaction, the SESSION

itself will be completed and the changes won’t be reflected in the table.

rollback transaction

Example for Nested Transactions:

--Points to remember: If any 1 of the inner transaction is rolled back, the outer transaction

cannot be committed.

--The outer transaction will be committed only when all the inner transactions are committed.

create table TestTran

(

cola int PRIMARY KEY,

colb varchar(50)

)

--Note: Using "with" keyword, we can give a message to the clients/ users. This is especially used

for marking a transaction.

--Example transaction with “with” keyword:

begin transaction OuterTransaction with mark

go

--This statements sets @TRANCOUNT to 1.

print N'Transaction count after BEGIN Outer Transaction is:' + cast(@@TRANCOUNT as

nvarchar(10))

Insert into TestTran values (1,'lena')

begin transaction InnerTransaction1


go

print N'Transaction count after BEGIN Inner Transaction1 is: ' +

cast(@@TRANCOUNT as nvarchar(10))

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Insert into TestTran values (2,'kishore')

begin transaction InnerTransaction2

go


print N'Transaction count after BEGIN Inner Transaction2 is:' +

cast(@@TRANCOUNT as nvarchar(10))

Insert into TestTran values (3,'sivaprasad')

commit transaction InnerTransaction2


print N'Transaction count after COMMIT Inner Transaction2 is:' + cast(@@TRANCOUNT

as nvarchar(10))

go

commit transaction InnerTransaction1


print N'Transaction count after COMMIT Inner Transaction1 is:' + cast(@@TRANCOUNT

as nvarchar(10))

go

commit transaction OuterTransaction


print N'Transaction count after COMMIT OuterTransaction is :' + cast(@@TRANCOUNT

as nvarchar(10))

go

--Example for deadlock condition and non-deadlock condition:



--case a)Non - deadlock scenario:

begin transaction DeadLock1

update cts.employee set address = 'Madras' where id=34620

--Syntax :waitfor delay 'time' will commit the transaction after the stipulated time

given.

waitfor delay '00:00:08' -- This will Commit the transaction after 8 seconds

update cts.employees set empname='M Chanakya' where empid=346232

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commit transaction Deadlock1

begin transaction Deadlock2


--Syntax :waitfor delay 'time' will commit the transaction after the stipulated time

given.




--case b) DeadLock Scenario:

begin transaction DeadLock1


--Syntax :waitfor delay 'time' will commit the transaction after the stipuled time given.




-- output for DeadLock1:

--(1 row(s) affected)


--Msg 1205, Level 13, State 51, Line 5

--Transaction (Process ID 62) was deadlocked on lock resources with another process and has

been chosen as the deadlock victim. Rerun the transaction.

begin transaction Deadlock2


--Syntax :waitfor delay 'time' will commit the transaction after the stipuled time given.




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--Output for DeadLock2:



--Note: If any error has occured during the process, just check @@trancount and ensure that it is

0 or not. If it is not 0, make it 0 by executing commit statement explicitly until the count becomes

0.

--Avoiding Deadlock using exceptional handling:

RETRY:

begin transaction TransEvent

begin try


--waitfor delay '00:00:15'


end try

begin catch

if ERROR_NUMBER() = 1205 -- Note: This error number deals with deadlock.

begin

goto RETRY

end

end catch

commit transaction TransEvent

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15.XML support in SQL Server

Points to remember:

XML means “Extensible Markup Language”.

SQL supports XML.

In SQL, a data type called “xml” is available for XML documents.

In XML, all the elements should be properly nested.

XML is case – sensitive. So be careful when using tags.

XML Modes:

There are four XML modes. Namely,

a) FOR XML RAW -- Columns in the table will become the attributes.

b) FOR XML PATH -- Each entry will be enclosed inbetween <row> and </row> tag

c) FOR XML AUTO -- The <row> tag is replaced by the table name

d) FOR XML_EXPLICIT

Note:

XML PATH (‘User_Defined_Name’) – Each entry will be enclosed inbetween the

<User_Defined_Name> opening and closing tag. The ‘User_Defined_Name’ can be

anything.

--Note: On executing below 3 statements, a link with the name <student/> will be shown. On

clicking it, a XML page will be opened inside the SQL.

declare @xmlVariable xml

set @xmlVariable='<student/>';

select @xmlvariable

--Create a Table with XML type

create table employeeXML

(

ID xml,

Name xml,

Language_known xml,

preferred_location xml,

Qualification xml

)

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--Inserting datas into the table

insert into employeeXML values

(N'<id>346238</id>',

N'<name>Lenaprasanna</name>',

N'<language_known>Telugu</language_known>',

N'<Preferred_Location>Hyderabad</Preferred_Location>',

N'<Qualification>BTech. CSE. </Qualification>')


(N'<id>346200</id>',

N'<name>Kishore</name>',

N'<language_known>Tamil</language_known>',

N'<Preferred_Location>Chennai</Preferred_Location>',

N'<Qualification>B.E. CSE. </Qualification>')


(N'<id>346534</id>',

N'<name>Chanakya</name>',



N'<Qualification>BTech. CSE. </Qualification>')


(N'<id>346538</id>',

N'<name>Sri Harsha Chilla</name>',



N'<Qualification>BTech. ECE. </Qualification>')


(N'<id>346345</id>',

N'<name>Sai Shiva Prasad</name>',



N'<Qualification>BTech. ECE. </Qualification>')

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--Using XML mode in XML table:

select * from employeeXML FOR XML RAW

select * from employeeXML FOR XML PATH

select * from employeeXML FOR XML PATH ('EmployeeTable')

select * from employeeXML FOR XML AUTO

--Using XML mode in normal table

SELECT * from cts.Customer FOR XML RAW

SELECT * from cts.Customer FOR XML PATH

SELECT * from cts.Customer for XML AUTO

--Note:

--creating XML document with many childs and sub-childs using XPATH may conserve lots of

space.

--Instead we can give them as an attributes.

--(ie.)

--Instead of using like this:

<Employees>

<Employee><id>346238</id><name>Lenaprasanna</name></Employee>

<Employee><id>346200</id><name>Kishore</name></Employee>

<Employee><id>346534</id><name>Chanakya</name></Employee>

</Employees>

--we can give like this:

<Employees>

<Employee id="346238" name="Lenaprasanna"/>

<Employee id="346200" name="Kishore"/>

<Employee id="346534" name="Chanakya"/>

</Employees>

--XQUERY methods in SQL:

1.value()--retreives the value that is present in the given path.

2.exist()--methods return 1 if the data exists in the XML structure.else it will return 0

3. query() –display all the elements with tags

4. node()—to access all the elements and access the values across the table.

5. modify()--To update the xml document content

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--Example for using the above methods:

a) USING VALUE() METHOD:

1.getting the values of the first user

declare @xmlvar xml

set @xmlvar='<Employees>





</Employees>'

select @xmlVar.value('Employees[1]/Employee[1]/@name','varchar(20)') as "First Employee

Name"

Output:

First Employee Name

----------------------

Lenaprasanna

2.getting the id of the second user

declare @xmlvar xml






</Employees>'

select @xmlVar.value('Employees[1]/Employee[2]/@id','varchar(20)') as "Second Employee ID"

Output:

Second Employee ID

----------------------

346200

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b) USING EXIST() METHOD:

1. Check whether the value exists or not:

Syntax:

--select XMLColumn_Or_XmlVariable.exist('The full path')

--case a) Check for existing record:

declare @xmlvar xml






</Employees>'

select @xmlVar.exist('/Employees/Employee[@id="346238"]') as "Is Exist?"

Output:

Is Exist?

-----------

1

--case b) Check for non-existing record:

declare @xmlvar xml






</Employees>'

select @xmlVar.exist('/Employees/Employee[@id="346538"]') as "Is Exist?"

Output:

Is Exist?

----------

0

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c)USING QUERY() METHOD:

1.Retreives all the entries of Employees/Employee tag

declare @xmlvar xml






</Employees>'

SELECT @xmlVar.query('/Employees/Employee') as Result1

Output:

Result1

-----------------------------------------

<Employee id="346238" name="Lenaprasanna" /><Employee id="346200" name="Kishore"

/><Employee id="346534" name="Chanakya" />

2.query that retreives distinct name

declare @xmlvar xml






</Employees>'

SELECT @xmlvar.query('distinct-values(data(/Employees/Employee/@name))') as "Distinct

names"

Output:

Distinct names

------------------------------

Lenaprasanna Kishore Chanakya

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e) USING NODE() METHOD:

1.Query that retreives all the id and name from the xml in a table form.

declare @xmlvar xml






</Employees>'

select x.value('@id','int') as "EmployeeID", x.value('@name','varchar(30)') as "EmployeeName"

from @xmlvar.nodes('/Employees/Employee') EmployeeXml (x)

Output:

EmployeeID EmployeeName

------------- ------------------------------

346238 Lenaprasanna

346200 Kishore

346534 Chanakya

346535 Lenaprasanna

2. Retreiving the attributes of the parent tag and also of the current tag.

declare @xmlvar xml


<Employee S.No="1">

<Details id="346238" name="Lenaprasanna"/>

</Employee>

<Employee S.No="2">

<Details id="346200" name="Kishore"/>

</Employee>

<Employee S.No="3">

<Details id="346534" name="Chanakya"/>

</Employee>

<Employee S.No="4">

<Details id="346535" name="Lenaprasanna"/>

</Employee>

</Employees>'

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select x.value('../@S.No','int') as "Serial Number",x.value('@id','int') as "EmployeeID",

x.value('@name','varchar(30)') as "EmployeeName" from

@xmlvar.nodes('/Employees/Employee/Details') EmployeeXml (x)

USING XML_EXPLICIT mode along with FOR XML :

-- Create table variables

declare @Employee table

(EmployeeID int NOT NULL,

FirstName varchar(30) NOT NULL,

LastName varchar(30) NOT NULL,

JobTitle varchar(50) NOT NULL)

--

declare @Language table

(LanguageID int NOT NULL,

LanguageName varchar(30) NOT NULL)

--

declare @EmployeeLanguage table

(EmployeeID int NOT NULL,

LanguageID int NOT NULL)

--

-- Populate table variables with sample data

insert into @Language values (1, 'English')

insert into @Language values (2, 'Spanish')

insert into @Language values (3, 'French')

insert into @Language values (4, 'Italian')

insert into @Language values (5, 'Greek')

--

insert into @Employee values (101, 'Jane', 'Doe', 'Accountant - Level I')

insert into @Employee values (102, 'John', 'Smith', 'Business Analyst')

insert into @Employee values (103, 'Erin', 'Thopmson', 'Database Administrator')

--

insert into @EmployeeLanguage values (101, 1)






--

-- Render as XML

select 1 as Tag,

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NULL as Parent,

NULL as 'Requisitions!1',

NULL as 'Record!2!EmployeeID!element',

NULL as 'Record!2!FirstName!element',

NULL as 'Record!2!LastName!element',

NULL as 'Record!2!JobTitle!cdata',

NULL as 'Languages!3!language!element'

union

SELECT 2 as Tag,

1 as Parent,

NULL,

EmployeeID,

FirstName,

LastName,

JobTitle,

NULL

FROM @Employee

union all

select 3 as Tag,

2 as Parent,

NULL,

e.EmployeeID,

e.FirstName,

e.LastName,

e.JobTitle,

l.LanguageName

from @Employee e

inner join @EmployeeLanguage el on e.EmployeeID = el.EmployeeID

inner join @Language l on el.LanguageID = l.LanguageID

order by 'Record!2!EmployeeID!element', 'Languages!3!language!element'

for xml explicit

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