Thursday, 12 May 2016

What is Self Join in SQL Server : Interview Question with Example

SQL Self Join : The SELF JOIN is used to join a table to itself as if the table were two tables, temporarily renaming at least one table in the SQL statement.

Lets first create table
Create Person table for Self Join example

create table tblPerson(P_ID int primary key, P_Fname varchar(20),P_Lnamevarchar(20),
Gender varchar(10),P_Father int,P_Mother int)
insert into tblPerson values('Puran','Singh','M',null,null)

Self Join Example:
select a.P_Fname,b.P_Fname from tblPerson as a
join tblperson as b on a.P_ID=b.P_Father
where a.P_Fname='ram'

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