SQLOne looks like a good idea:
"SQLOne Console 3.0 - Automatic SQL conversion utility to translate SQL queries between the dialects used by Oracle, SQL Server, DB2, Informix, Sybase, MySQL, PostgreSQL, and pure ANSI SQL. Looks very useful indeed if you need to support multiple back ends. Trial version is limited to converting 50 queries, contact them for pricing. "
[via Larkware]
Though the "contact them for pricing" seems a bit scary. That usually means something costs a lot.
PS
I use a question mark at the end of titles when :
a. I talk about something that I haven't checked out myself yet.
b. My title is a question.