On: Best practices for writing SQL queries

[yardstick]

> Although it’s possible to join using a WHERE clause (an implicit join), prefer an explicit JOIN instead, as the ON keyword can take advantage of the database’s index.

Don’t most databases figure this out as part of the query planner anyway? Postgres has no problems using indexes for joins inside WHERE.

[Hjfrf → yardstick]

Yes all databases will use indexes for joins. There's quite a few mistakes like that.

My guess is the author heard something about not using implicit inner joins (deprecated decades ago) and misunderstood.

E.g. This old syntax- SELECT * FROM a, b WHERE a.id = b. a_id