Depends vs. Pre-Depends

[Tonnesen Steve <tonnesen@cmsd.bc.ca>]

I am developing a package which uses a Mysql database.  I would like to
create the database and populate it with some data during the postinst
script.  If I add the following Dependencies:

Depends: mysql-server
Depends: libdbd-mysql-perl
Depends: libdbi-perl

Can I be certain that Mysql and DBD/DBI will be installed and configured
before my postinst script runs?  If I can't, would it be better to bomb
out of my postinst script until the next run, or use a Pre-Depends?

Steve Tonnesen
tonnesen@cmsd.bc.ca