Forum OpenACS Q&A: MySQL Gotchas - a link for PG/MySQL questions...
One example that jumped out at me: if you turn on the InnoDB type tables, you can drop any table, even one referenced by another table, i.e. you can break foreign key constraints with impunity. And you need to turn on InnoDB... in order to get transactions.
and 1.13 - date columns accept, eg. 2003-02-31
grr - why do so many of my clients INSIST on mysql :(