Creating rnd data on a single table is easy, I don't really need a tool for that. However, it would be extremely useful to have a tool able to creata test data

Creating rnd data on a single table is easy, I don't really need a tool for that. However, it would be extremely useful to have a tool able to creata test data using actual relations between tables in the DB (e.g. generate fake users, then use their User IDs to generate 1-10 random posts for each user. Then for each posts I want a couple of random comments attached. And so on and on...)