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MS SQL Server MS SQL Server 20052005

Lab # 4 : Practicing Queries, part #2

Complex Queries

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2. Complex Queries

WHERE Clause Form:

USE database_nameSELECT Column_List[ INTO New_table ]From table1[table2,….][ WHERE conditions ][ GROUP BY group_by_expression ][ HAVING search_conditions ][ ORDER BY order_expression[ASC|DESC] ]

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Subqueries

An Outer query contains an Inner query, which can be included in the WHERE Clause or in the FROM Clause

Outer Query:SELECTFROMWHERE (Inner Query)

Outer Query:SELECTFROM (Inner Query)

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Subqueries And Comparison Operators

Example :Q:Q: View all Employees First & Last name who work in Innovation Department

A:A:Use CompanySelect FName, LNameFrom Employeewhere DNO=( Select DNumber

From Department Where DName=‘Innovation’)

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Subqueries And Comparison Operators

Example :Q:Q: View all Employees Last name who work on project Building

A:A:Use CompanySelect LNameFrom Employeewhere SSN IN( Select ESSN

From Works_On Where PNO IN(SELECT PNumber

From Project WHERE

PName=‘Building’)) Can we Substitute the IN clause with = ?

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Subqueries (Inner Query included in FROM Clause)

Example :Q:Q: View all Employees Last name who their SSN is greater than 1000

A:A:Use CompanySelect LNameFrom (Select *

From Employee Where SSN>1000) AS NewEmp

Should I give the inner query result a name?

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Subqueries ( ANY & ALL Operators )

ANY:ANY: Returns true if the result of an inner query contains at least one row that satisfies the comparison

ALL:ALL: Evaluates true if the evaluation of the table column in the inner query returns all values of that column

Syntax :

Outer_query column operator [ANY | ALL] Inner_query

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Subqueries ( ANY & ALL Operators )

Example :Q:Q: View the oldest Employees SSN who their BDate is less than all other employees

A:A:Use CompanySelect SSNFrom Employeewhere Bdate>=ALL (Select BDate

From Employee)

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EXIST Function

Checks the inner query of a subquery and evaluates to true if its result contains at least one row

Syntax:[NOT] EXISTS (query)

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EXIST Function

Q:Q: View all employees info only if there is an employee who’s salary is 5000

A:A:

Use CompanySelect *

From Employeewhere Exists (Select *

From Employee

Where salary=5000)

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GROUP BY Clause

Defines one or more columns as a group such that all rows within any group have the same values for those columns

ALL columns specified in the SELECT clause must appear in the GROUP BY clause

If an aggregate function appears in the SELECT clause, then you can’t include a simple column in it unless if its used in the Group By clause

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GROUP BY Clause

Q:Q: For each Project View all employees SSN with hours working on more than 20 hours

A:A:

Use CompanySelect PNO,Hours,ESSN

From Works_Onwhere hours>20

Group by PNO,Hours,ESSN

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GROUP BY Clause

Example :

Q:Q: How many Employees works in each project?A:A:

Use CompanySelect PNumber ,COUNT(*)

emp_count

From Works_IN

Group by PNumber

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HAVING Clause

Defines conditions that is then applied to groups of rows (Such as WHERE Clause condition applied on rows) and its Syntax: HAVING condition

Q:Q: Get Project numbers for all projects employing less than four persons

A:A:Use CompanySelect PNOFrom Works_OnGroup by PNOHaving Count(*)<4

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HAVING Clause

Example :

Q:Q: View Projects names that their name starts with SA: A:

Use CompanySelect PName

From Project

Group by PName

HAVING PName LIKE ‘S%’

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ORDER BY Clause

Defines the order of the rows in the result and its Syntax: ORDER BY [col_name | col_no [ASC | DESC]] , …

Q:Q: Get employees all info ordered by their SSN

A:A:

Use CompanySelect *

From Employee

Order BY SSN

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ORDER BY Clause

Q:Q: Get employees first & last names ordered by their last name then their first name

A:A:

Use CompanySelect FName, LName

From Employee

Order BY LName, FName

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ORDER BY Clause

Q:Q: Get employees first & last names ordered by their last name Ascending and then their first name Descending

A:A:

Use CompanySelect FName, LName

From Employee

Order BY 2 Asc, 1 DESC

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INTO Clause

It performs two parts:1. Create a new table with columns as same the

columns specified in the select clause2. Insert the rows that matches the query into the

new table

Basic INTO form:Use database_nameSelect columns_ListINTO NewTableNameFrom table(s)

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INTO Clause

Q:Q: Create a separate table for all employees who aren’t supervised

A:A:

Use CompanySelect *INTO Head_Supervisors

From Employee

Where MGRSSN IS NULL

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Set Operators

UPDATE table_name SET column_name = newValueWHERE condition

EX.UPDATE employee SET Salary=32400WHERE SSN=2341

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Set Operators

UnionUnionis the set of all elements appearing in either or both of tablesForm: Query_1 UNION [ALL]Query_2 …ALL option includes all resulting rows including duplicates are to be displayed

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Set Operators ( UNION)

Q:Q: View all employees numbers who either belong to department 5 or work on their project more than 20 hours in ascending order of employee number

A:A:Use CompanySelect SSNFrom EmployeeWhere DNO=5

UNIONSelect ESSNFrom Works_OnWhere Hours>20Order By 1

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Set Operators

INTERSECTIONINTERSECTION is the set of all elements belongs to both of the tables

Form: Query_1 INTERSECT Query_2 …

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Set Operators ( INTERSECT)

Q:Q: View all employees numbers who belong to department 5 and work on their project more than 20 hours in ascending order of employee number

A:A:Use CompanySelect SSNFrom EmployeeWhere DNO=5

INTERSECTSelect ESSNFrom Works_OnWhere Hours>20Order By 1

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Set Operators

DIFFERENCEDIFFERENCEis the set of all elements belongs to the first table but doesn’t belong to the second table

Form: Query_1 EXCEPT Query_2 …

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Set Operators (EXCEPT)

Q:Q: View all employees numbers who belongs to department 5 except those who work on their project more than 20 hours in ascending order of employee number

A:A:Use CompanySelect SSNFrom EmployeeWhere DNO=5

EXCEPTSelect ESSNFrom Works_OnWhere Hours>20Order By 1

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CASE Expression

CASE Basic form:CASE Basic form:CASE expression_1

{WHEN exp_2 THEN result_1}{ELSE result_n}

END

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CASE Expression

Q:Q: View all employees SSN,FNAME,Lname and Grade as following:Salary Employee Grade:0-6000 1 , 6000-15000 2 , 15000-22000 3 ,

>22000 4A:A:

Use CompanySelect SSN,FNAME,LNAME, CASE

when Salary>0 and Salary<=6000 Then 1when Salary>6000 and Salary<=15000 Then 2when Salary>15000 and Salary<=22000 Then 3ELSE 4

END Employee_GradeFrom Employee

Column name after END

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COMPUTE Clause

Uses aggregate function(Min, Max,…) to calculate summary values that appear as additional rows in the result of query

Basic COMPUTE form:

Use database_nameSelect columns_List

From table(s)

Where condition

COMPUTE aggre_Func(column_name)

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COMPUTE Clause

Q:Q: View all employees numbers, project their working on, and working hours for employees work on project 3 or 10. And view the minimum working hours

A:A:

Use CompanySelect *

From Works_on

Where PNO=3 OR PNO=10

Compute MIN(Hours)

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COMPUTE Clause (Using BY option)Q:Q: View all employees numbers, project their working

on, and working hours for employees work on project 3 or 10. And view the minimum working hours for each project

A:A:Use CompanySelect *From Works_onWhere PNO=3 OR PNO=10Order By PNOCompute MIN(Hours) BY PNO

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COMPUTE Clause(Multiple aggregate function)Q:Q: View all employees numbers, project their working on,

and working hours for employees work on project 3 or 10. And view the minimum, maximum, avrage working hours

A:A:

Use CompanySelect *

From Works_on

Where PNO=3 OR PNO=10

Compute MIN(Hours), MAX(Hours), AVG(Hours)

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COMPUTE Clause

SELCET INTO is not allowed (because the result of the COMPUTE clause is not a table)

All columns in the COMPUTE clause must appear in the SELECT list

The name of each column in the COMPUTE BY clause must appear in the ORDER BY clause

The order of the columns in the COMPUTE BY & ORDER BY clauses must be identical