mysql - convert this INNER JOIN to UNION

Question

I can not get this to work. I want to convert this query to UNION to remove OR in notifies 's INNER JOIN.

SELECT posts.status, posts.reports, posts.private_id,
    enter code hereposts.parent_id, posts.post_id,
    posts.reply_counts, posts.sender, posts.content, 
    posts.image, posts.thumb, posts.date,members.username, 
    members.avatar,members.avatar_path,members.level, members.state 
FROM posts
INNER JOIN members ON posts.sender = members.member_id 
INNER JOIN notifies ON (
    posts.post_id=notifies.post_id OR posts.parent_id=notifies.post_id
) 
WHERE  (posts.date>notifies.last_date AND posts.sender<>1) 
    AND notifies.member_id=1 
    AND posts.private_id<>0 
    AND posts.status=1 
    AND posts.reports<3  
ORDER BY posts.last_update DESC, posts.date DESC LIMIT 0,25;

my try that not working:

(SELECT posts.status, posts.reports, posts.private_id , posts.parent_id, 
    posts.post_id, posts.reply_counts, posts.sender, posts.content, 
    posts.image, posts.thumb, posts.date, members.username, members.avatar,
    members.avatar_path,members.level, members.state 
FROM posts 
INNER JOIN members ON posts.sender = members.member_id 
INNER JOIN notifies ON posts.parent_id=notifies.post_id) 

UNION

(SELECT posts.status, posts.reports, posts.private_id , posts.parent_id,  
    posts.post_id, posts.reply_counts, posts.sender, posts.content, 
    posts.image, posts.thumb, posts.date, members.username, members.avatar,
    members.avatar_path,members.level, members.state 
FROM posts 
INNER JOIN members ON posts.sender = members.member_id 
INNER JOIN notifies ON posts.post_id=notifies.post_id) 
WHERE  (posts.date>notifies.last_date AND posts.sender<>1) 
    AND notifies.member_id=1 
    AND posts.private_id<>0
    AND posts.status=1 
    AND posts.reports<3  
ORDER BY posts.last_update DESC, posts.date DESC LIMIT 0,25;

Answer 1

It seems that you only added the where clause to the last section of the UNION, and not to both.

So you went from

SELECT *
FROM  A INNER JOIN
B ON (a.ID = b.ID OR a.ID = b.ID2)
WHERE tada

to

SELECT *
FROM  A INNER JOIN
B ON (a.ID = b.ID)
UNION
SELECT *
FROM  A INNER JOIN
B ON (a.ID = b.ID2)
WHERE tada

So you need to do something like

SELECT *
FROM  A INNER JOIN
B ON (a.ID = b.ID)
WHERE tada
UNION
SELECT *
FROM  A INNER JOIN
B ON (a.ID = b.ID2)
WHERE tada

Answer 2

You don't have to change this to a union to make it more efficient. Here is an alternative version (only the from and where clauses shown):

FROM   posts 
       INNER JOIN members 
               ON posts.sender = members.member_id 
       LEFT JOIN notifies n 
               ON ( posts.post_id = n.post_id ) 
       LEFT JOIN notifies np 
               ON ( posts.parent_id = np.post_id ) 
WHERE  ( (posts.date > n.last_date or posts.date > np.last_date)) AND posts.sender <> 1 ) 
       AND (n.member_id = 1 or np.member_id = 1)
       AND posts.private_id <> 0 
       AND posts.status = 1 
       AND posts.reports < 3 

This also removes a duplicate row when both the parent and the post match.

I'm not positive that the date comparison is doing exactly what you want but it should be close.