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 Transact-SQL (2008)
 foreign key
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ergot72
Starting Member

1 Posts

Posted - 01/17/2013 :  05:41:49  Show Profile  Reply with Quote
I have a database set up sort of like this

Table1(id, ...)
Table2(id, ...)
Comment(id, typeId, str)

where typeId=1 means Table1 and typeId=2 means Table2

what I want to do is to create foreign keys to Table1 and Table2 from Comment
sort of
ALTER TABLE Comment ADD CONSTRAINT FK_Comment_Table1 FOREIGN KEY(id, typeId) REFERENCES Table1 (id, 1);
ALTER TABLE Comment ADD CONSTRAINT FK_Comment_Table2 FOREIGN KEY(id, typeId) REFERENCES Table2 (id, 2);

Is it possible?
If not, how should I set up the relations?

visakh16
Very Important crosS Applying yaK Herder

India
52317 Posts

Posted - 01/17/2013 :  05:55:43  Show Profile  Reply with Quote
nope not possible.
only way to do this would be to enforce this referential logic by means of trigger/check constraint.

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

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ScottPletcher
Constraint Violating Yak Guru

USA
366 Posts

Posted - 01/17/2013 :  18:54:25  Show Profile  Reply with Quote
You could try adding a TypeID column to Table1 and Table2, and then using that column name in the FK definition.
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