How to write into a mysql session variable?

Hi all,

I'm just starting to develop reportsand dashboards in Pentaho, so sorry if this is something obvious. I have tried to find information on it but have been unable to.

I'm trying to write into a mysql session variable everytime I need to query the database. I have tried modifying the connection so it executes a set command, tried xactions, execute a set just before the sql, but have been unable to.

Some process in the database is expecting those variables, so I need to execute something like this just before querying the database:
set @snapshot_date := '2014-12-28';

Coul you please give me some pointers on how to do something like that?

Thanks and regards?