it's ok, no problems. im not saying tht u can't
change between these two RDBMS. Even i had experience
of changing  between these two, but in my case i have
changed my system from MS SQL Server to MySQL

there i had difficulties like,

1. I have used Views, Triggers, Stored Procedures a
lot in my system so i have no option other than making
it in pure java while changing it from SQL Server to
MySQL.

2. In SQL commands i hv used datetime functions which
is available in different format(syntax) in MySQL so
tht also i did in pure java / some of them changed to
MySQL syntax.

3. Backup & Restoring syntax also different in these
i make these changes also.

these are some of the difficulties which i faced
(which almost took 10-15 sleepless nights frm me to do
all the changes req),

but hope for the best in ur case...