For some reason, last time I searched on google it didn't showed me anything useful (on any of the first 4 pages), but this time, I got the answer I needed. Solutions: 1. Use a different user then SYSTEM. I didn't though at this, after all I didn't wanted to complicate things on a learning project. 2. Filter each group using %. When I tried it before it didn't worked, but now after I started the DB again, the filter worked as it should have. Maybe there was an error connecting to the DB, don't know, it's good that now it is working.