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Re: SSE 2008: Referring to Other Rows Being Added

Cross-posted to 2 groups.

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A simple/simpler solution would be to always sort the values. In other
words, to enforce that A is always lower or equal to B, both in the
table and whenever you do inserts. That way you don't need two rows for
each pair. In the table, this can be enforced with CHECK (a <= b)

-- 
Gert-Jan



Gene Wirchenko wrote:
> 
> Dear SQL'ers:
> 
>      How do I force a condition based on multiple rows?  I want the
> necessary rows to be entered in a batch.  As a simple example, what
> would be the coding of the constraint in this case following?
> 
>           create table Symmetric
>            (
>            a int not null,
>            b int not null
>            )
> 
>      Constraint: If (x,y) is in Symmetric, then (y,x) is also in
> Symmetric.
> 
>      Anyone adding rows would have to do it in a batch:
>           insert into Symmetric
>            (a,b)
>           values
>            (3,5),
>            (5,3)
> 
>      I am hoping that there is a simple answer that I am overlooking.
> Right now, all I can think of is to scan both Symmetric and the batch
> (Inserted).
> 
> Sincerely,
> 
> Gene Wirchenko

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Thread

SSE 2008: Referring to Other Rows Being Added Gene Wirchenko <genew@ocis.net> - 2011-07-12 13:20 -0700
  Re: SSE 2008: Referring to Other Rows Being Added Erland Sommarskog <esquel@sommarskog.se> - 2011-07-12 23:55 +0200
    Re: SSE 2008: Referring to Other Rows Being Added Gene Wirchenko <genew@ocis.net> - 2011-07-12 15:37 -0700
      Re: SSE 2008: Referring to Other Rows Being Added Erland Sommarskog <esquel@sommarskog.se> - 2011-07-13 10:16 +0200
  Re: SSE 2008: Referring to Other Rows Being Added Gert-Jan Strik <sorrytoomuchspamalready@xs4all.nl> - 2011-07-13 19:39 +0200
    Re: SSE 2008: Referring to Other Rows Being Added Gene Wirchenko <genew@ocis.net> - 2011-07-13 12:14 -0700

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