# Semi Join with Examples in Relational Algebra, Database Systems

## Semi-Join with Examples in Relational Algebra (Database Systems)

Today, in this fresh and new article, we will cover the following topics;

1. What is Semi Join?
2. Examples of Semi Join

### What is Semi Join?

Semi-JoinÂ matches the rows of two relations and then show the matching rows of the relation whose name is mentioned to the left side ofÂ â‹‰ Semi Join operator. I am describing the more details in the below examples. Hopefully, it will help you to understand the semi-join.

### Example 1 of Semi Join

 ID Rank Salary 101 Assistant Professor 80,000 102 Associate Professor 90,000 103 Lecturer 70,000

Table 1: Teacher

 ID RollNo Marks 103 2017 – 01 80 104 2017 – 02 90 105 2017 – 03 70

Table 2: Student

 ID RollNo Marks 103 2017 – 01 80

Table 3: Student â‹‰ Teacher ORÂ Student Semi Join Teacher

 ID Rank Salary 103 Lecturer 70,000

Table 4:Â Teacher â‹‰ Student OR Teacher SEMI-JOIN Student

### Example 2 of Semi Join

 ID Rank Salary 101 Assistant Professor 80,000 102 Associate Professor 90,000 103 Lecturer 70,000

Table 5: Teacher

 ID RollNo Marks 101 2017 – 01 80 103 2017 – 02 90 106 2017 – 03 70

Table 6: Student

 ID RollNo Marks 101 2017 – 01 80 103 2017 – 02 90

Table 7:Â Student â‹‰ Teacher OR Student SEMI-JOIN Teacher:

 ID Rank Salary 101 Assistant Professor 80,000 103 Lecturer 70,000

Table 8:Â Teacher â‹‰ Student OR Teacher SEMI-JOIN Student

## Example 3 of Semi Join

 Employee Name EmpId DeptName Sameed 1 CS Shahzeb 2 SE Abid 3 CS Shamil 4 IT
 Department DeptName Manager SE Shahzeb IT Shamil
 EmployeeÂ â‹‰Â Dept Name EmpId DeptName Shahzeb 2 SE Shamil 4 IT

Topic Covered

Semi-Join with Examples in Relational Algebra, Database Systems.

Prof.Fazal Rehman Shamil (Available for Professional Discussions)
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