What I did to get better at 'big' queries was start by writing out things like inner queries as CTEs, Table Parameters, or (if in oracle, lol) refCursors. That

What I did to get better at 'big' queries was start by writing out things like inner queries as CTEs, Table Parameters, or (if in oracle, lol) refCursors. That's (sometimes!) less performant than the one big query, but you can then refactor into a single query if you so choose. Yeah, it's slow goings at first, but you get pretty good at SQL in the process.