基本的MySQL问题：如何从一个表中获取不在另一个表中的行？

Question

I have a list of usernames (with a column called "username") + other info in my "users" table.

I also have another list of usernames (with a column called "username") in my smaller "recentusers" table.

How can I create a mysql query to get all the usernames that are in the "users" table but not in the "recentusers" table?

I know it is probably very simple, but any help would be appreciated!

Answer 1

select username from users where username not in (select username from recentusers)

Then after the first username add in the other information you want to select as well.

As pointed out by OMG Ponies, this query will run as fast as using Left Join or Is null.