How can I assign a "select [value] from [db_table]" value to a single variable?

I'm trying the new database connector, and I'm using an Oracle DataBase, and I want to assign a single value into a Bonita's defined value (int, bool) and when I do it, the process stops to work. When I retrieve a list of values and I assign it to an Array List, I don't have any problem, but when I want to work with single values, I can't do that, please help me.

PD: Sorry for my English