sql UNION breaks query - mysql

Question

Query :
(
SELECT
upd.uid,
upd.update_id,
upd.update,
upd.date,
upd.type,
upd.total_likes,
upd.total_comments,
upd.deleted,
usr.username AS `username`,
usr.profile_picture AS `profile_picture`
,(
SELECT
COUNT(lik.id)
FROM
likes as lik
WHERE
upd.update_id = lik.item_id
AND
lik.uid = 118697835834
AND lik.type=0
) as liked_update,
(
SELECT
COUNT(fav.id)
FROM
favorites as fav
WHERE
upd.update_id = fav.item_id
AND
fav.uid = 118697835834
AND fav.type=0
) as favorited_update
FROM
updates AS upd
LEFT JOIN
users AS usr
ON upd.uid = usr.uid
WHERE
upd.deleted=0
AND
(
upd.uid=118697835834
OR EXISTS
(
SELECT *
FROM
subscribers AS sub
WHERE
upd.uid = sub.suid
AND sub.uid = 118697835834
)
)
)
UNION
(
SELECT
topic.uid,
topic.tid,
topic.title,
topic.body,
topic.total_likes,
topic.total_replies,
topic.views,
topic.date,
usr.username AS `username`,
usr.profile_picture AS `profile_picture`
,(
SELECT
COUNT(lik.id)
FROM
likes as lik
WHERE
topic.update_id = lik.item_id
AND
lik.uid = 118697835834
AND lik.type=1
) as liked_update,
(
SELECT
COUNT(fav.id)
FROM
favorites as fav
WHERE
topic.update_id = fav.item_id
AND
fav.uid = 118697835834
AND fav.type=1
) as favorited_update
FROM
topics AS topic
LEFT JOIN
users AS usr
ON topic.uid = usr.uid
WHERE
topic.deleted=0
AND
(
topic.uid=118697835834
OR EXISTS
(
SELECT *
FROM
subscribers AS sub
WHERE
topic.uid = sub.suid
AND sub.uid = 118697835834
)
)
)
ORDER BY date DESC
I have added the UNION ( SELECT ) and the query takes forever to load and finally it stops returning a blank page...
removing UNION ( SELECT ) works fine...

Answer 1

OK after all the comments can you please say what changes you made to get the script working.
In light of your comment about the data from two tables being in the same columns that is because you have told the engine to do that by using UNION. If you want them in seperate columns you will need to place Nulls in between:
SELECT
upd.uid,
upd.update_id,
upd.update,
upd.date,
upd.type,
upd.total_likes,
upd.total_comments,
upd.deleted,
null AS `topicuid`,
null AS `topictid`,
null AS `topictitle`,
null AS `topicbody`,
null AS `topictotal_likes`,
null AS `topictotal_replies`,
null AS `topicviews`,
null AS `topicdate`,
usr.username AS `username`,
usr.profile_picture AS `profile_picture`,
(SELECT COUNT(lik.id) FROM likes as lik WHERE upd.update_id = lik.item_id AND lik.uid = 118697835834 AND lik.type=0) as liked_update,
(SELECT COUNT(fav.id) FROM favorites as fav WHERE upd.update_id = fav.item_id AND fav.uid = 118697835834 AND fav.type=0) as favorited_update
FROM
......
UNION ALL
SELECT
null AS `upd.uid`,
null AS `upd.update_id`,
null AS `upd.update`,
null AS `upd.date`,
null AS `upd.type`,
null AS `upd.total_likes`,
null AS `upd.total_comments`,
null AS `upd.deleted`,
topic.uid,
topic.tid,
topic.title,
topic.body,
topic.total_likes,
topic.total_replies,
topic.views,
topic.date,
usr.username AS `username`,
usr.profile_picture AS `profile_picture`,
(SELECT COUNT(lik.id) FROM likes as lik WHERE topic.update_id = lik.item_id AND lik.uid = 118697835834 AND lik.type=1) as liked_update,
(SELECT COUNT(fav.id) FROM favorites as fav WHERE topic.update_id = fav.item_id AND fav.uid = 118697835834 AND fav.type=1) as favorited_update
You might need to do a bit more work on the column names but you should get there. You should read up on what the UNION operator actually does to two or more queries.

Answer 2

When you use UNION you have to have exact same results "column format, names,..." so you have at top of query upd.total_comments as total_comments, and bottom you have topic.total_replies as total_replies those are different names. hope you understand what i try to explain, if not visit here where it explains better.