I meant to reply to a different comment originally, specifically the one including this quote from Torvalds:

> Good programmers worry about data structures and their relationships.

> -- Linus Torvalds

I was specifically thinking about the "relationship" issues. The worst messes to fix are the ones where the programmer didn't consider how to relate the objects together - which relationships need to be direct PK bindings, which can be indirect, which things have to be cached vs calculated live, which things are the cache (vs the master copy), what the cardinality of each relationship is, which relationships are semantically ownerships vs peers, which data is part of the system itself vs configuration data vs live, how you handle changes to the data, (event sourcing vs changelogging vs vs append-only vs yolo update), etc.

Not quite "data structures" I admit but absolutely thinking hard about the relationship between all the data you have.

SQL doesn't frame all of these questions out for you but it's good getting you to start thinking about them in a way you might not otherwise.