(i)Select:

• The select operator is used to select the rows from a table which satisfy particular selection condition given in selection operation.

• Select operator selects a set of tuples that satisfy a selection condition.

• Output of query is exactly same as input schema of table.

• This is unary relational operator having only one input table.

Syntax:

σ<attribute_name><comparison_operator><constant_value>(<input_table_name>)

Where,

Attribute_name: Name of the column in table

Comparison_operator: =,<,<=,>,>=,<>

Example:

Select all the employees having age below 25 years

     σage<25(Employee)

ii) Project

• Project operator is used foe selecting some of many columns in table to display in result set.

• Few rows and columns can be selected as per requirement.

• This unary relational operator having only one input table.

Syntax:

         π<column_list>(<input_table_name>)

Example:

Find Employees salary from Employee table and Salary

         πEid,Salary,Age(Employee)

ii) Natural Join

• A Natural join returns all rows by matching values in comman columns having same name and data type of columns should be presentin both sides

Example:

Find all the Employees and their department name

Employee Table

Department Table

        πeid,dname(Employee ⋈ Department)

iv) Set Intersection

• Set Intersection operator finds out all rows that are common in both result of Query 1 and in the result of Query 2.

Syntax: (Query Expression 1) ⋂ (Query Expression 2)

R

S

R ⋂S

Examples:

All Employees in IT Department under Mumbai University

IT_Employee

All Employess in ABC College

Intersection of the above is employees in IT Department of ABC College