I'm searching for a tool that allows me to explicity declare a couple of databases, each one with a query and compare the results periodically. Something like DiffKit seems to follow this concept, but it is not been developed anymore.
EDIT: I want to able to compare data from different DBMS's (say MySQL and Oracle). I want to compare the table content. Compared tables can have different table schemas, so the tool must provide a way to match and compare those tables columns.