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.