Do you always have to join tables on their id? SQL

[h1lo]

Just wondering because I’m always doing it.

[adamgaffney96]

You can join tables on any field that you like depending on the context. As long as the field is in both tables and is a unique identifier in one of those tables, then it’s completely fine to join on that. However generally you cannot always predict if something will be a unique identifier or not and that’s what you add an id field, so that every row in a table can always be uniquely identified.

[lisalisaj]

It might be helpful to read up on PRIMARY and FOREIGN keys.
https://www.essentialsql.com/what-is-the-difference-between-a-primary-key-and-a-foreign-key/

and, here:
https://dataschool.com/learn-sql/joins/