5 ms·
No, left joins were intended here. They mean different things. With inner joins the semantics are the same. If the performance is different, the database que
by btilly 7y ago
No, left joins were intended here. They mean different things.
With inner joins the semantics are the same. If the performance is different, the database query optimizer is broken.
- gtsteve 7y agoI see, apologies. However, I'm reasonably certain we'd see poor performance with that query on MySQL 5.7, but I don't think it's got as good an optimiser as Postgres for example.
- btilly 7y agoI can't say that MySQL doesn't perform poorly. But if so, then their optimizer is more broken than I though. Even SQLite figures this one out and does it right.