[thelist] server side validation

[George Klingenhoffer]

I'm working on a mailing list feature; how do I check for duplicate email
addresses in the Access database while adding if it does not exist or throw
up an error message if it does.

Would that require two SQL statements?  One to query every address and
compare the address to be added to each address in the database then one to
add the address or is there a single SQL statement for this?  Thanks!