union select. different amount of rows

[Jaynesh]

Hello

 

How would I do a union select if each query had a different amount of rows? I tried adding NULL but that does not seem to work.

[Kustom_Vegas]

you will want to use a join..

 

http://dev.mysql.com/doc/refman/5.0/en/join.html

[Jaynesh]

Hi,

 

I'm already using a join on each query. Will it still work? Can I add an OR to merge both queries?

 

For e.g

 

SELECT user.id, post.id

FROM user

LEFT JOIN

ON user.id = post.id

 

OR

 

SELECT vote.id, vote.up, vote.down

FROM vote

[Kustom_Vegas]

just list the table references like so

 

SELECT * FROM t1 LEFT JOIN (t2, t3, t4)
                 ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c) //taken from dev.mysql

[Jaynesh]

Hello

 

Ok, i've done that but it isnt working.

 

SELECT DISTINCT dbPosts.post
FROM dbPosts

LEFT JOIN ( dbUsers, dbFriends )
ON (
dbPosts.username_id = dbUsers.id
AND (dbPosts.username_id = dbFriends.user_id)
OR
(dbPosts.username_id = dbFriends.friend_id))

LEFT JOIN (dbUsers, dbPosts_share, dbFriends)
ON (
dbPosts.username_id = dbUsers.id
AND 
(dbPosts.post_id = dbPosts_share.post_id)
OR 
(dbPosts.username_id = dbPosts_share.user_id)
AND
(dbPosts_share.user_id = dbFriends.friend_id)
OR 
(dbPosts_share.user_id = dbFriends.user_id))