What Is self-join In Sql?

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Staff asked 2 months ago

What Is self-join In SQL? What is the requirement of self-join?

Can anyone give some appropriate description with an example?

Answers (1)

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Tabish Rangrej Marked As Accepted
Staff answered 2 months ago

As the name defines, when the table is joined to itself then it’s called SELF JOIN. it is like each row of the particular table is joined with itself and other rows depend on some conditions. in easy words join between two copies of the same table.

Syntax

SELECT T2.coulmn1 , T2.column2
FROM Table1 T2, Table2 T2
WHERE some_condition(s);

Below is an example.

following is the Employee table and its data.

 

Following is Self Join Query…

SELECT A.EmpName AS Employee_Name1, B.EmpName AS Employee_Name2, A.City
FROM [dbo].[Employee] A, [dbo].[Employee] B
WHERE A.EmpId <> B.EmpId
AND A.City = B.City
ORDER BY A.City;

 

above is the resulting self-join. where we are joining the same table and put condition.

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