Joining three tables to one query

[Coly010]

I'm a bit confused on what type of JOIN to use for this.

I have three tables, all containing the column USERID. I want to join them all together into one query so that i can place them into an array.

Right so i want the row from the tables as long as the userid is the same between them all.

Do i use inner join, left join, right join, full join? (what even is the difference) and how would i arrange it in a query?

thanks for any help

[Guest]

You missed out natural join ^_^.

I would use inner join, if one of the tables doesn't contain data it won't return anything, left and right join simply adds the data to left or right side of the main table.

I believe that's how it works,

[Coly010]

Okay, so when doing it, do I:

SELECT u.*, t.*, a.* FROM user u INNER JOIN table t ON u.userid = t.userid INNER JOIN another_table ON u.userid = a.userid WHERE u.userid = $userid

Should that work?

[Seker]

Found this site, which diagrams it for a visual comparison. Worth a look.

http://www.khankennels.com/blog/index.php/archives/2007/04/20/getting-joins/

[Coly010]

Still can't really get my head wrapped around the "matches" part of it. does it only take the row from the other table which has the same column name and value as all the column names in the first table? Or does it give you the full row if as long as one column matches a certain column in the other table?

inner join didnt work, left join did work :S

Edited January 7, 2014 by !Angel

[Guest]

INNER won't work if there is no data in any of the other tables that relate.