Question

I’m trying to write a stored procedure and depending on a certain column value, I want to be able to change what table I select from. I’ll try to give an example:

SELECT ItemNumber,        ItemType,         Description FROM  CASE ItemType WHEN 'A' THEN TableA ELSE TableB END  WHERE   CASE ItemType WHEN 'A' THEN ItemNumber = @itemNumber ELSE PartNumber = @itemNumber END 

As you can see, not only am I dynamically changing the table I select from, but since these two tables were made at two different times by two different people, the column names are different as well.

So, my question is: What is the best way to accomplish this, since SQL Server doesn’t seem to like my query I have constructed.

If anyone who sees what I’m trying to do can suggest a better way to do this, I’d be all ears 🙂

Answer 1

You can not use CASE statement in FROM clause, but you can use the following instead:

SELECT itemnumber, itemtype, description   FROM tablea  WHERE itemnumber = @itemnumber AND itemtype = 'A' UNION ALL SELECT itemnumber, itemtype, description   FROM tableb  WHERE partnumber = @itemnumber AND itemtype <> 'A'