Explain select, project and division operations with examples.

Explain select, project and division operations with examples. (RGPV 2019)

Ans. Select operations : Select operation displays the records for the condition. Select operation is denoted by sigma (σ).

Syntax: 

σcondition(TableName)

Example:

RollNo	Name	Brach
012	Jayesh	CSE
013	Kunal	ME
015	Dipali	EC

Input:

σName=Jayesh(Student)

Output:

RollNo	Name	Brach
012	Jayesh	CSE

Project operation : Project operations displays the specific column of a table. Projection operation is denoted by pie (∏).

Syntax: 

∏_ColumnName (TableName)

Example:

RollNo	Name	Brach
012	Jayesh	CSE
013	Kunal	ME
015	Dipali	EC

Input:

∏_RollNo (Student)

Output:

RollNo

012

013

015

Division operations : 

Division operations involves dividing one relation by another.  The division operator is used for division operations.

Student
RollNo	Brach
012	CSE
013	ME
015	EC
019	CSE
021	CE
034	AI

Branch

Brach

CSE

ME

EC

Student / Branch

RollNo

012

019

In above example, when the division operation is performed, it will retrieve only those RollNo from relation "Student" who has branch “CSE” from relation Branch.