Unit2 RDBMS and Basic SQL.pdf

7/28/2019 Unit2 RDBMS and Basic SQL.pdf

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Unit 2: Basic SQL

Pratian Technologies (India) Pvt. Ltd.www.pratian.com


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Overview

UNIT 1 Introduction to RDBMSRelational DBMS

UNIT 2 Introduction to SQL

DDL Create, Alter, Drop, Truncate

UNIT 3 Data Manipulation Language

Basic SQLCopyright 2010 Pratian Technologieswww.pratian.com

DML Insert, Update, Delete, Transactions Commit, Rollback


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Overview

UNIT 4 Select StatementsSelect statement Where clause

Like, Logical operators, In and between predicates

Null, Not null, Aggregate functions

Order by

Group By



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UNIT 1


Introduction to RDBMS


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Relational DBMS

RDBMS is a model in which all data is logicallystructured with relations

Data is stored in tables

It is a two dimensional table with special propertiesStudents Table

StudentId Name Age CourseId


Courses Table

1002 Raghav K 21 2

CourseId Course

1 Basic SQL

2 Excel


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Relational DBMS

Rows Tuples [collection of records]

Each record contains same fields

Columns Attributes Domain specific

Different types of data exist mainly - Character,Numeric, DateStudId

Name Age JoinDate Fees CourseId


1001 Krishna S 19 05/14/2010 1000 1

1002 Preethi J 21 05/15/2010 2000 2

1003 Sriram V 21 05/15/2010 1200 1

CourseId Course

1 Basic SQL

2 Excel


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Relational DBMS - Properties

Entries of column and row values have to be singlevalued

Entries of attributes [columns] are of same kind

No two rows are identical


Order of rows and columns are unimportant

Every column has to be uniquely defined


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Relational DBMS Database Schema

Organization of information within database for single ormultiple users

Store of data that describes the content and structure ofphysical data store


v u y ,relationships, access controls etc..


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Relational DBMS - Architecture

Software to process queries/programs

DBMS

Application Programs/Queries

Users

DATABASE

SYSTEM


Stored Data Defn. Stored Database

Software to access stored data


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Application Programmers Responsible for writing application programs that use the

database

End Users

Interact with the system from workstations or terminals. A givenend user can access the database via one of the applications

Administrators

Relational DBMS - Users


One who manages the database centrally Decides on the type of internal structures and relationships

Ensures security of the database

Controls access to data through codes and passwords

Can restrict views or operations users can perform on database


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Relational DBMS Data Integrity

Data integrity Refers to wholeness and roundness of the database

Achieved by using integrity constraints and domain constraints

Primary Key Uniquely identify a particular record

Foreign Key


CourseId is the foreign key here

Stud_Id Name Age CourseId

1 Krishna 19 1

2 Radha 21 2

CourseId Course

1 SQL

2 Excel


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Summary

Understand database concepts

Know characteristics of a DBMS

Understand Relational DBMS concepts



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UNIT 2


Introduction to SQL


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What is SQL?

SQL stands for Structured Query Language

Simple, powerful and standard data access languagefor relational database management systems


s a spec a ze anguage or up a ng, e e ng anrequesting information from databases


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Standard SQL Statement Groups

Group Statements Description

DQL SELECT DATA QUERY LANGUAGEUsed to get data from database

DML INSERTUPDATEDELETE

DATA MANIPULATIONLANGUAGEUsed to add or change databasedata


ALTERDROPTRUNCATE

Used to manipulate databasestructures and definitions

DAL GRANT

REVOKE

DATA ADMINISTATION

LANGUAGEUsed to grant and revoke accessrights to database objects


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Data Types in SQL

Data type Description

CHAR(n) To store fixed length string. Maximum length = 255bytes

VARCHAR(n) To store variable length string. Maximum length =

255 bytesTEXT or BLOB To store maximum length of 65535 characters.

Binary Large Objects Text, images, files etc..

TINYINT If signed: -128 to 127. If unsigned: 0 to 255. You


can specify a width of up to 4 digits.

SMALLINT If signed : -32768 to 32767. If unsigned : 0 to65535. You can specify a width of up to 5 digits.

INT If signed : -2147483648 to 2147483647. Ifunsigned : 0 to 4294967295. You can specify a

width of up to 11 digits.


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Data Types in SQL

Data type Description

FLOAT(M,D) You can define the display length (M) and thenumber of decimals (D). Decimal precision can goto 24 places for a FLOAT.

DOUBLE(M,D) You can define the display length (M) and thenumber of decimals (D). Decimal precision can go

to 53 places for a FLOAT.

DATETIME A date and time combination in MM/DD/YYYY


HH:MM:SS format, between 01/01/1000 00:00:00and 12/31/9999 23:59:59. For example, 3:30 in theafternoon on December 30th, 1973 would be

stored as 12/30/1973 15:30:00


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Creation of Database Objects - DDL

Table Tables are objects which store data

A table can have a maximum of 1000 columns

Syntax

CREATE TABLE table_name


({col_name col_datatype [[CONSTRAINTconst_name][col_constraint]]}

[table_constraint],

)[AS query]


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Example

CREATE TABLE Students

(StudentId int,

Name varchar(100),

JoinDate date


); CREATE TABLE Courses

(

CourseId int,

Course varchar(50)

);


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Naming of tables

Name of the table must begin with a letter A-Z or a-z. It maycontain numerals and the special character _ (underscore)

It can be 30 characters in length


It must not be a SQL reserved word


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Specifying Integrity Constraints

A database is said to be integrated if the values in thedatabase are correct according to a set of rules

Checking of consistency must be carried out to ensuredata integrity


y uintegrity constraints


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Specifying Integrity Constraints

Types of Constraints

Column constraints associated with a single column

Table constraints associate with more than one column


If not named, will be automatically generated by DBMS


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Types of Integrity Constraints

NOT NULL

UNIQUE

PRIMARY KEY


FOREIGN KEY


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NOT NULL CONSTRAINT

User will not be allowed to enter null values

Example:


(


,

Name varchar(100) NOT NULL,

JoinDate date NOT NULL

);


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DEFAULT CLAUSE

To specify a default value for an attribute if no value isgiven

Example:



StudentId int,Name varchar(100),

JoinDate date,

City varchar(100) DEFAULT BANGALORE

);


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UNIQUE CONSTRAINT

The keyword UNIQUE specifies that no two records canhave the same attribute value for a column

Example:

CREATE TABLE Courses


CourseId int,Course varchar(50) UNIQUE

);


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PRIMARY KEY CONSTRAINT

A primary key constraint enables a unique identification ofeach record in a table

Example:



StudentId int NOT NULL IDENTITY(1,1),

Name varchar(50),

JoinDate date,

PRIMARY KEY (StudentId)

);


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FOREIGN KEY CONSTRAINT

This constraint specifies a column or list of columns as aforeign key of the referencing table

Referencing table is called Child table, referenced tableis called Parent table

Example:



(

StudentId int NOT NULL PRIMARY KEY IDENTITY,

Name varchar(100),CourseId int FOREIGN KEY REFERENCES Courses(CourseId)

);


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MODIFYING A TABLE

The ALTER command is used to modify an existing table

Syntax:

ALTER TABLE table_name

[ADD (col_name col_datatype col_constraint,..)] |


_ _ _ _ _

[ADD (table_constraint)] |

[DROP CONSTRAINT constraint_name] |

[DROP COLUMN existing_col_name];


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MODIFYING A TABLE

ADD clause The ADD clause is used to add a column or a constraint to an

existing table

ALTER clause The ALTER clause is used to modify existing columns of a table


DROP clause DROP clause is used to remove columns or constraints from a

table


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MODIFYING A TABLE

Example: -- To add a column

ALTER TABLE Students ADD Location varchar(100) DEFAULTBANGALORE;

-- To change the data type for a column

ALTER TABLE Courses ALTER COLUMN Course varchar(100);


-- To make a column unique ALTER TABLE Courses ADD CONSTRAINT uq_Course

UNIQUE(Course)

-- To rename a column in a table

Exec sp_rename Courses.Course , Courses.CourseName, Column

-- To drop a column

ALTER TABLE Students DROP COLUMN JoinDate;


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DROP A TABLE

To remove the definition of a table from the databaseDROP TABLE command is used

Example:

DROP TABLE Courses;



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Summary

Understand SQL as the standard language for interactingwith relational database

Know the type of SQL statements

Understand DDL statements to create relational tables



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UNIT 3


Data Manipulation


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DATA MANIPULATION

DML Data Manipulation Statements are used to makechanges to the data stored in a table

The manipulations that can be performed on a table are Add

Data is inserted into table using INSERT statement


Update

Any modifications to table data are made usingUPDATE statement

Delete

Table data is deleted using DELETE statement


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INSERT STATEMENT

INSERT statement is used to add new data into the table

Syntax:

INSERT INTO table_name[(col_name1, col_name2,)]

{VALUES (value1, value2, ) | query };


Example: INSERT INTO Courses (CourseId, Course)

VALUES (2, EXCEL);


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INSERT STATEMENT

Insert using query output Example: [CoursesOffered is another table with fields as Courses]

INSERT INTO Courses (CourseId, Course)

SELECT * FROM CoursesOffered



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INSERT STATEMENT GENERAL RULES

Values should match data type of the respective columns

Number of values should match the number of column

names mentioned

All columns declared as NOT NULL should be supplied


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Character strings should be enclosed in quotes

DATE values should be enclosed in quotes


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UPDATE STATEMENT

Update statement is used when we need to modify data ina table

Syntax: UPDATE {table_name | alias}

SET col_name = value |

=


_

[WHERE Condition];

UPDATE STATEMENT


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UPDATE STATEMENT

Update all rows UPDATE Students

SET JoinDate = 10/17/2010;

Update only certain rows

UPDATE Students

SET JoinDate = 10/17/2010


WHERE Name = Krishna;

Update multiple columns

UPDATE Students

SET JoinDate = 10/17/2010, Name = Krishna S

WHERE StudentId = 2;

DELETE STATEMENT


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DELETE STATEMENT

DELETE statement is used to delete rows from a table

Syntax:

DELETE [FROM] {table_name | alias }[WHERE Condition];


DELETE FROM Students

Delete particular row from table

DELETE FROM Students WHERE StudentId = 2

S


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Summary

We know how to manipulate data in a table using DMLcommands

Know how to save or undo changes made to table data



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UNIT 4


SELECT STATEMENT

SELECT STATEMENT


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SELECT STATEMENT

We will be looking at the following

SELECT STATEMENT

How to retrieve data from tables

Column aliases

Where clause


SELECT STATEMENT - more options Logical operators AND, OR, NOT

IN

BETWEEN

IS NULL / IS NOT NULL

GROUP BY / ORDER BY

SELECT STATEMENT


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SELECT STATEMENT

Syntax:

SELECT [ALL | DISTINCT ] { * | col_name,..}

FROM table_name alias

[WHERE expr1]

[CONNECT BY expr2 [START WITH expr3]]

[GROUP BY expr4] [HAVING expr5]


[UNION | INTERSECT][ORDER BY expr | ASC | DESC];

COLUMN ALIAS AND DISTINCT


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COLUMN ALIAS AND DISTINCT

Select Statement to get all columns SELECT * FROM Students;

Select Statement to get specific columns

SELECT StudentId, Name FROM Students;


SELECT StudentId, Name, JoinDate JoiningDateFROM Students;

DISTINCT To get unique values

SELECT DISTINCT Name FROM Students;

WHERE CLAUSE


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WHERE CLAUSE

WHERE Clause Where clause is used to do selective retrieval of rows

Rows which meet search condition are returned

WHERE

List of Operators

=


Not equal to

< Less than

> Greater than

= Greater than equal to

WHERE CLAUSE


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WHERE CLAUSE

To get all rows where join date is equal to a date SELECT * FROM Students WHERE JoinDate = 10/17/2010;

To get all rows where StudentId is greater than 2

SELECT * FROM Students WHERE StudentId > 2;

T ll r w wh r in i r r h n r l


a date SELECT * FROM Students WHERE JoinDate >= 10/17/2010;

LIKE PREDICATE


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LIKE PREDICATE

The pattern contains a search string along with otherspecial characters % and _

An underscore(_) in the pattern matches exactly onecharacter


z

characters It cannot match a NULL

LIKE PREDICATE


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LIKE PREDICATE

To list all students whose name begins with K SELECT Name

FROM Students

WHERE Name LIKE K%;

To list all students whose name begins with K and thirdletter I


SELECT Name

FROM Students

WHERE Name LIKE K_I%;

LOGICAL OPERATOR


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LOGICAL OPERATOR

A logical operator combines the results of two componentconditions to produce a single result based on them orinvert the result of a single condition

NOT Returns true if condition is false, returns false ifcondition is true


AND Returns true if both component conditions are true,returns false if both component conditions are false

OR Returns true if either component condition is true,returns false if both component conditions are false

LOGICAL OPERATOR


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LOGICAL OPERATOR

NOT SELECT Name FROM Students WHERE NOT StudentId = 2;

AND

SELECT Name FROM Students

WHERE StudentId > 1 AND JoinDate >= 10/17/2010;


OR SELECT Name FROM Students

WHERE Name = Krishna OR StudentId = 2;

IN PREDICATE


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IN PREDICATE

To select rows from defined set of values

SELECT *

FROM Students

WHERE Name IN (Krishna, Radha);


BETWEEN PREDICATE


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BETWEEN PREDICATE

To retrieve rows which meets the range of values given

SELECT * FROM Students

WHERE JoinDate

BETWEEN 10/17/2010 AND 10/20/2010;


NULL PREDICATE


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U C

NULL predicate is used to check if an attribute or acolumn is null.

Col_name = NULL cannot be done

IS NULL

SELECT * FROM Students WHERE JoinDate IS NULL


IS NOT NULL SELECT * FROM Students WHERE Name IS NOT NULL

AGGREGATE FUNCTIONS


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Produces a single value for an entire group

Functions are

COUNT()

Produces the number of rows query has selected

AVG()

Produces the average of all selected values of a given column

MAX()


Produces the largest of all selected values of a given column

MIN()

Produces the smallest of all selected values of a given column

SUM()

Produces the arithmetic sum of all selected values of a givencolumn

GROUP BY


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The GROUP BY clause is used to group selected rowsand return a single row of summary information

Each group of rows are based on the values of theexpression(s) specified in the GROUP BY clause


u u u

GROUP BY


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Example: SELECT CourseId, sum(Fees)

FROM Students

GROUP BY CourseId

SELECT CourseId, sum(Fees)

FROM Students


GROUP BY CourseId

HAVING CourseId IS NOT NULL

ORDER BY


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ORDER BY clause is used to sort records

The sort is done on the column in either ascending ordescending order. [ASC default]

Example:


tu ents

ORDER BY NAME

Summary


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Know how to use the SELECT statement to retrieve datafrom a table

Know the options to be used with SELECT statement forconditional data retrieval


w w u v u

Know how to sort data

Question Time


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Please try to limit the questions to the topics discussed during the session. Thank you.


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