>When the user enters a new unit, or modifies the current one, I need to save it. But I don't want it to save if the unit is a duplicate. I also want to be the one to give the error message.
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>Currently, I have a complicated IF to determine if the unit has changed and then I scan through the table to see if it's already there. I also have to make sure I don't get an error if the user changes the unit name, then changes it back, because then it will have changed AND be in the table already.
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>It seems like there should be a simpler way of doing this. I've made the unit name a candidate index. Can I do the row update and have it tell me if the key's uniqueness was violated?
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>Is there some way to put this in the database so whenever a user tries to save a duplicate unit, my error message comes up an the save is rejected?
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>Thanks,
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>-Michelle

I think Candidate Tag is normal solution here.