[Solved] Can referential integrity be enforced using alter table?

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I’m not sure I understand why you think this is better than foreign keys, but yes, you can implement referential integrity in other (inferior) ways. These will be slower than doing it right and fixing the design.

  1. Check constraint + UDF

     CREATE FUNCTION dbo.IsItAValidWeight(@Son_Weight int)
 RETURNS bit
 WITH SCHEMABINDING
 AS
 BEGIN
   RETURN 
   (
      SELECT CASE WHEN EXISTS 
      (
        SELECT 1
        FROM no.Man WHERE Weight = @Son_Weight
      ) THEN 1 ELSE 0 END
   );
 END
 GO

 ALTER TABLE no.Man WITH CHECK 
   ADD CONSTRAINT chk_Son_Weight 
   CHECK dbo.IsItAValidWeight(Son_Weight) = 1;

  2. Trigger

    Need to know a lot more about the schema I think, but you can research.

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solved Can referential integrity be enforced using alter table?