OT: seeking query help, where?

First, sorry for the OT, flame me off-list!

I'm a sysadmin being impressed into dba service. i've been getting along
pretty well writing queries and making reports, but i've got some questions.
suggestions for a good list/forum for help?

from two tables both with email_addr columns, i want a distinct list of all
email_addrs in one column. what i do now is select distinct on each and then
sort -u the results.

thanks in advance
-t