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Self Join example and please do explain it

 
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TS70363

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Joined: 07 Apr 2010
Posts: 94
Location: Bangalore, India

PostPosted: Thu Apr 22, 2010 11:17 am    Post subject: Self Join example and please do explain it
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Hi,,

Can some one provide me with an example of self join and explain it...
I tried so much but could not find some relevant material on it...
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guptae

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Joined: 14 Oct 2005
Posts: 1187
Location: Bangalore,India

PostPosted: Thu Apr 22, 2010 1:31 pm    Post subject:
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Hello There,

Self join is just like any other join except that two instances of the same table will be joined together.

Lets take an example of EMPLOYEE Table which contain rows for each employee in the organisation . Employee can be Manager as well.

Table contain follwoing columns

EMPLOYEE Table
Empid Int
Mgrid Int
Dept Char(25)
Salary Double
Empname Char(35)

So in order to find out the manager of all the Employees u need a self join

Code:
SELECT t1.empname [Employee], t2.empname [Manager]
FROM emp t1, emp t2
WHERE t1.mgrid = t2.empid
 
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