XPost: microsoft.public.sqlserver.programming   
   From: sorrytoomuchspamalready@xs4all.nl   
      
   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   
      
   --- SoupGate-Win32 v1.05   
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