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I need to assure that a value is unique in two columns (this is not a “two columns” index issue).
Table A
Column A1 Column A2
Memphis New York -> ok
San Francisco Miami -> ok
Washington Chicago -> ok
Miami Las Vegas -> Forbidden ! Miami already exists
Is it possible ?
My example is with cities but don’t focalize on that. My real need is about generated hexadecimal ids.
You need to add a constraint trigger that looks it up after insert/update.