Right join vs left join, which table is left vs right?

Question

Given

select * 
from a
left join b
on a.id = b.id

is table a left and table b right?

Would that be equivalent to

Select *
from a
right join b
on b.id = a.id

because I switched left and right while flipping the ON clause? Or is a still left because it came first and b is right because it's the thing we're joining?

Thank you.

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Does this answer your question? [Which table exactly is the "left" table and "right" table in a JOIN statement (SQL)?](https://stackoverflow.com/questions/4109704/which-table-exactly-is-the-left-table-and-right-table-in-a-join-statement-s) — philipxy, Apr 15 '20 at 23:42

score 2 · Accepted Answer · answered Apr 15 '20 at 17:16

No. "left" and "right" refer to the ordering of the tables in the FROM clause. So these are equivalent:

select * 
from a left join
     b
     on a.id = b.id

select * 
from b right join
     a
     on a.id = b.id

These two on clauses do exactly the same thing:

on a.id = b.id
on b.id = a.id

They do not affect the results at all.

Right join vs left join, which table is left vs right?

1 Answers1