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How do I maintain referential integrity when updating lookup tables

Database Programming

How do I maintain referential integrity when updating lookup tables

by  hilfy  Posted    (Edited  )
Situation: You have a table (lookup table) with two (possibly more) fields Code, Description. The Code field is used in one or more other tables (master table(s)) to point to the description.

Problem: You want to change one of the Code fields, but it is already being used in one or more master tables.

Solution 1: If there are no referential integrity constraints in the database, you can just update the Code field and update the value for that field in the master tables.

Solution 2: If there are referential integrity constraints, you have to go through a little more complicated process (steps MUST be done in this order.)

1. Add a new record to the lookup table with the new code and the old description.
2. Update all of the records in the Master table(s) to have the new code. A simple sql template for this is:
Code: 
  update MasterTable
  set CodeField = NewValue
  where CodeField = OldValue
3. Delete the record with the old code from the lookup table.
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