Trying :

        select * from mytable <sqltest mylist multiple type=int column=id>

did not work, it generates a ProgrammingErrorProgrammingError: (1064, "You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near '<sqltest mylist multiple type=int column=id> LIMIT 1000'")

My problem was that I tried to test my Z SQL method through the ZMI, testing with a python script worked fine with the following Z SQL method :
SELECT *
FROM MyTable
<dtml-sqlgroup where>
  <dtml-sqltest mylist column=id type=int multiple>
</dtml-sqlgroup>
I also modified the "mylist" parameter declaration to specify that it is a list of integers which is set to none if no parameter is passed.

       liste:list:int=none

Thanks for your reply