Assume that we need to join two tables based on some condition. For example,
SELECT users.id, accounts.name from users, accounts where users.account_id = 1 AND users.account_id = accounts.id
SELECT users.id, accounts.name from users INNER JOIN accounts on accounts.id = users.account_id where users.account_id = 1
Both queries do the same. we are saving 3 words in the first query (this might help you to save 9 secs for every join you make).
Check the query plan for both of these queries, It will be same. I’ve checked this with MySql and Pgsql. I hope this will work in most of the DBMS systems. Let me know if you have any tricks like this.