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case in joining table

Author

Topic

mk_garg20
Constraint Violating Yak Guru

343 Posts

Posted - 2004-09-21 : 20:23:54

Hi All,
When i am joining 2 tables, can i use "case" statement in join.

example:-
SELECT .....
FROM table1 inner join table2 on (case when .. then .. end)

thanks

mk_garg

timmy
Master Smack Fu Yak Hacker

1242 Posts

Posted - 2004-09-21 : 20:52:31

Yes you can. It will be slow, though...

mk_garg20
Constraint Violating Yak Guru

343 Posts

Posted - 2004-09-21 : 20:57:57

Allright!
Here are my tables

lodgment
----------
jobnumber
runnumber
amount
type

conract
-------
jobnumber
runnumber

What i want is if lodgment.type is "P" then join on (jobnumber) else (jobnumber and runnumber)

Please tell me what will be syntax.

Thanks

mk_garg

timmy
Master Smack Fu Yak Hacker

1242 Posts

Posted - 2004-09-21 : 21:42:57

Ah - wasn't quite what I had in mind, but here goes:

SELECT L.JobNumber, IsNull(C1.RunNumber, C2.RunNumber) as RunNumber
FROM lodgment L LEFT JOIN conract C1 ON L.jobnumber = C1.jobnumber AND L.type = 'P'
                LEFT JOIN conract C2 ON L.jobnumber = C2.jobnumber 
                                    AND L.runnumber = C2.runnumber
                                    AND L.type <> 'P'

Or you could do it this way (although I wouldn't recommend...)

SELECT L.JobNumber, C.RunNumber
FROM lodgment L INNER JOIN conract C ON 
                (CASE WHEN L.Type = 'P' THEN Convert(varchar, L.jobnumber) 
                     ELSE Convert(varchar, L.jobnumber) + ';' + Convert(varchar, L.runnumber)
                END) = 
                (CASE WHEN L.Type = 'P' THEN Convert(varchar, C.jobnumber) 
                     ELSE Convert(varchar, C.jobnumber) + ';' + Convert(varchar, C.runnumber)
                END)

mk_garg20
Constraint Violating Yak Guru

343 Posts

Posted - 2004-09-22 : 00:25:51

Thanks Timmy,
It is really helpfull.

mk_garg

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