>Nadya,
>
>Just to put a concrete example together for lurkers:
>
>

>LookupId  LookupType  LookupValue
>1         Color       Red
>2         Color       Green
>3         Color       Blue
>4         Flavor      Sweet
>5         Flavor      Sour
>

>
>If you have a table that has a column for the item's color and it's FK constrained only on table.ColorNo = Loopup.LookupId then it would be possible for an item to have a color of "Sour".
>
>The FK constraint needs to have the LookupType included in the constraint so that only the Color rows are valid ColorNo values.
>
>>>FK constraints on lookups are every bit as critical. If you use a single overloaded lookup table you need to ensure that you constrain the lookuptype for a given FK into the lookup.
>>>
>>>>In this question I was more concerned about lookup tables. Of course, for real parent and child we must have triggers in place. I do agree with having them for lookup as well, but want to find out the general practice.
>>
>>That was originally implemented with very fanky indexes. We changed the indexes, but left the constrains. So, you're right, they don't make much sense now!
>>
>>Thanks for helping me in realizing that.

That's exactly our case. We eliminated the indexes which used alltrim(upper) in the filters expressions, but now we can not use the triggers. I'm going to write a message to our team explaining the problem, though I already mentioned this issue to two of my colleagues.