Question

I have two tables, users and messages.

users has the fields userId(int) and username(string) and
messages has the fields userId(int) and message.

I have the username, and want to grab all messages related to that username’s userId.

Would the join function work in this case (and if so, how?), or would I have to make two separate queries?

Answer 1

SELECT       m.*
FROM         messages m
  INNER JOIN users u
  ON         m.userId = u.userId
WHERE        u.username = 'UsernameHere';

Use an INNER JOIN to reference the user table from the messages table (matching [referencing] them both by the userId column)

And an example of the query can be found here: http://www.sqlfiddle.com/#!8/bc3ce/3/0