PostgreSQL - INNER JOIN vs WHERE, which one will perform better?

Question

I've just made a quick search through the web but couldn't find exactly what I'm looking for.

How much efficient an INNER JOIN is comparing to a regular WHERE statement?

I have a couple of queries in PostgreSQL that need to use some tables (say four or five) "linked" together by key/foreign key conditions. To implement those queries I'm using the WHERE clause to join all the required tables.

I wonder if any performance gains will bd achieved if I re-write those queries with the INNER JOIN clause (instead of a WHERE clause).

Answer 1

I think what you mean to say is difference between the below queries

select a.col1,b.col2 from table1 a, table2 b where a.id = b.id;

Against

select a.col1,b.col2 from table1 a
join table2 b on a.id = b.id;

To my knowledge, both are doing a INNER JOIN; it's just that the above one is a old style, hard to read, error prone implicit join syntax and the below one is recommended explicit join syntax.

So, I don't see any performance gain/loss here; since either way they are performing the same thing.