Thanks for the message.

First let me say this is a commercial software package, I DID NOT DESIGN THE DB.

Yes the WHERE clause represents the index (there is another statement that DOES work called by my system) and this one works manually.

And YES this Unique index allows NULL value on that column and therein I coalesce this. I will look at that part again. And again I did not design a DB that allows a NULL value within a unique index!!!I hardly ever allow NULL regardless let alone a move like that. You should see some of the stuff I have accounted for. Tables with no PK and they enforce PK within the .net app. So to merge I have a table (ImpliedPK) and one for foreign keys as well where not defined in the DB but enforced in code. I could go on but I think you get the point.