Tag Archives: SQL

Not Every “Not Equals” is Equal

Yesterday I voted on the poll by @SQL Daily about using different forms for “not equals” conditions and that brought back bad (and funny) memories. Over 25 years I have always used “!=”. “Does it matter”, you might ask? Actually, it shouldn’t. But here is my story and the reason, why I was considering to change my habits and use “<>”.

Continue reading

Subquery Unnesting – if it doesn’t work

Actually, the CBO usually does a good job optimizing “NOT IN” subqueries. Unless something goes wrong. Recently it took a long time on a database to search for the reason. At last looking in the CBO trace files (event 10053) has given the right hint.
Continue reading