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Finding duplicate keys
Message
From
14/01/1999 12:13:08
 
 
To
14/01/1999 12:09:50
General information
Forum:
Visual FoxPro
Category:
Databases,Tables, Views, Indexing and SQL syntax
Miscellaneous
Thread ID:
00176022
Message ID:
00176034
Views:
29
>>>>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.
>>>>
>>>>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.
>>>>
>>>>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?
>>>>
>>>>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?
>>>>
>>>>Thanks,
>>>>
>>>>-Michelle
>>>
>>>I think Candidate Tag is normal solution here.
>>
>>Candidate Tag? Is that different than making a field a candidate key? If not, and since it's already a candidate key, I don't see how that's a solution...
>>
>No, it's the same :). What's wrong you found? When you try to save a record, VFP will raise uniqueness violation error and you may trap it nicely.

I guess I'm not clear on error trapping. Do I do something like this:

ON ERROR llNotSaved = .T.
TABLEUPDATE()
IF llNotSaved
*Error message
ON ERROR

?

Thanks,

-Michelle
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