How to prevent column b containing the same value as any column a in Oracle?
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by Janek Bogucki
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Published on 2010-04-23T15:56:06Z
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2010/04/23
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Oracle
|data-integrity
What is a good way to prevent a table with 2 columns, a and b, from having any record where column b is equal to any value in column a? This would be used for a table of corrections like this,
MR -> Mr
Prf. -> Prof.
MRs -> Mrs
I can see how it could be done with a trigger and a subquery assuming no concurrent activity but a more declarative approach would be preferable.
This is an example of what should be prevented,
Wing Commdr. -> Wing Cdr.
Wing Cdr. -> Wing Commander
Ideally the solution would work with concurrent inserts and updates.
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