It is actually not that bad if instead of a single query, you do one query per table. It even offsets some of the burden to the app, which is generally easier

It is actually not that bad if instead of a single query, you do one query per table. It even offsets some of the burden to the app, which is generally easier to scale than the database. The idea is that you query the "root" table, loop over the results and build an array of IDs, then do additional queries to the other tables with a "where whatever_id IN (...)".