Using sub query

Sub queryA query inside another query

Examples of Subqueries

Example 1

Retrieve the name of all employees who have dependents

Example 1(continued)

In this example: the sub query is used in the where clause.

The example goal: to retrieve the ssn for the employees who have at least one dependent.

Example 2Retrieve the name of all employees who works on two projects

Example 2In this example: the sub query is used in the having clause

The example goal: to retrieve the number of projects for each employee who works on at least one project in the works_on table.

Example 3Retrieve the name of all employees with the department name each employee works on.

Example 3In this example: the sub query is used in the select clause.

The example goal: to retrieve the name of the department that each employee works on.

Example 4Retrieve all employees who works on all projects

Example 5Update the location of all projects controlled by Headquarter department to be in New york

Before update After update

Example 6Delete all employees in works_on table who works on all the projects located in Belliare

After deleteBefore delete

Backup and restore a database

Backup a databaseStep 1

Backup a databaseStep 2: click ok to backup

The location for the backed up database

Restore a databaseStep 1:

Restore a databaseStep 2: choose from device

Restore a databaseStep 3: add the database backup you want to restore

Restore a databaseStep 4: choose the location of the database backup you want to restore.

Restore a databaseStep 5: Now press OK for the last two interfaces

Check the check box

Choose your database

Restore a databaseStep 6: add the red colored text before the database location to correct the location of the database

C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data\clinic.mdf

C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data\clinic_1.LDF

Restore a databaseStep 7: Now your database created successfully

The restored database