little sql syntax question

If I have a table with 3 columns(a,b,c), and I want to check the distinct values of 2 of out of the three, (to see if the remaining values are duplicated, assuming one of them is a primary key, although perhaps an ill-defined one in theory), I can do a couple of things. I could temporarily put a unique index on the remaining columns to see if it succeeds.
Or, I could do a select count(distinct(b||c)) from table A; (to compare it with the count of the table). This is my question.. why the ||? It would seem I can't do a select distinct (b,c) from A. Am I really reduced to a string comparison? Or is there another way? Hope this isn't to obfuscated...

Thanks,
Dc. Received on Sat Apr 15 2000 - 00:00:00 CDT