My 10 second experiment shows both sections of the union query using
the best index in each case. Possibly more efficient if both datasets
contain duplicates, as only one of each record will be sent across
the network. On the downside, you need to wait for both queries to be
run before you get the information back.

I would only use it if the fields matched up between the two queries.

> Yes. I was just curious if running the two as a union, vs running

them

> separately and tallying details in the client will cause any

optimization or

> other problems.