MySQL syntax issue, multiple SELECT statements - mysql

Question

I am working of a project that has 2 tables as follows: users_fb and posts
I spent 3 hours playing with the code and then I gave up.
table: posts
+-----+---------+---------+---------+---------+-----------+
| id | by_user | by_page | votes | status | time |
+-----+---------+---------+---------+---------+-----------+
| 1 | 1 | 0 | 20 | 1 | 372041014 |
+-----+---------+---------+---------+---------+-----------+
table: users_fb
+-----+-----------+-------+---------+--------+-------+
| id | username | name | gender | fb_id | email |
+-----+-----------+-------+---------+--------+-------+
SELECT username,
(
SELECT COUNT(b.by_user)
FROM users_fb a LEFT JOIN posts b ON a.id = b.by_user
WHERE b.by_page = '0'
GROUP BY a.username
) AS totalCount ,
(
SELECT IFNULL(SUM(b.votes),0)
FROM users_fb a LEFT JOIN posts b ON a.id = b.by_user
GROUP BY users_fb.id
) AS total_votes
FROM users_fb ORDER BY total_votes DESC
The desired output
+-------------------+-------------+-------------+
| username | totalCount | total_votes |
+-------------------+-------------+-------------+
| user4 | 1 | 25 |
| user1 | 0 | 0 |
| user2 | 0 | 0 |
| user3 | 0 | 0 |
+-------------------+-------------+-------------+
UNFORTUNATELY: This is what I am getting
+-------------------+-------------+-------------+
| username | totalCount | total_votes |
+-------------------+-------------+-------------+
| user4 | 1 | 25 |
| user1 | 1 | 25 |
| user2 | 1 | 25 |
| user3 | 1 | 25 |
+-------------------+-------------+-------------+
If you need any further information, let me know. Thanks for your help.

Answer 1

You don't appear to have anything to join your tables together to match up with posts / votes go with which user.
Something like this should do it
SELECT users_fb.username, Sub1.postcount, Sub2.votecount
FROM users_fb
LEFT OUTER JOIN(
SELECT a.username, COUNT(*) AS postcount
FROM users_fb a
INNER JOIN posts b
ON a.id = b.by_user
WHERE b.by_page = '0'
GROUP BY a.username
) Sub1
ON users_fb.username = Sub1.username
LEFT OUTER JOIN(
SELECT users_fb.id, IFNULL(SUM(b.votes),0) AS votecount
FROM users_fb a
LEFT JOIN posts b
ON a.id = b.by_user
GROUP BY users_fb.id
) Sub2
ON users_fb.id = Sub2.id
Possibly simplified to
SELECT a.username, SUM(IF(b.by_page = '0', 1, 0)) AS postcount, IFNULL(SUM(b.votes),0) AS votecount
FROM users_fb a
LEFT JOIN posts b
ON a.id = b.by_user
GROUP BY a.username

Answer 2

Since you are doing no matching of the selects (i.e. there is no binding WHERE between them), MySQL has no wait to make them show together.
You should do something like this:
SELECT username, totalCount.count, total_votesGROUPED.sum
FROM users_fb
LEFT JOIN (
SELECT COUNT(b.by_user) as count, a.username
FROM users_fb a LEFT JOIN posts b ON a.id = b.by_user
WHERE b.by_page = '0'
GROUP BY a.username
) AS totalCount ON totalCount.username = users_fb.username,
(
SELECT IFNULL(SUM(b.votes),0) as sum, id
FROM users_fb a LEFT JOIN posts b ON a.id = b.by_user
GROUP BY users_fb.id
) AS total_votesGROUPED ON total_votesGROUPED.id = users_fb.id
ORDER BY total_votes DESC
If I had a bit more information, I could test it

Answer 3

Quite a few problems, the biggest is that you don't make any join between your "main query" and your "subqueries".
So finally, something like that should be better.
SELECT
a.username,
SUM (CASE WHEN b.by_page IS NOT NULL and b.by_page = '0' then 1 else 0 end) as cnt,
SUM (IFNULL(b.votes),0) as nbVotes,
FROM users_fb a
LEFT JOIN posts b ON a.id = b.by_user
GROUP BY users_fb.id

Answer 4

SELECT a.username,
COUNT(b.by_user) totalCount,
SUM(IFNULL(b.votes,0)) total_votes
FROM users_fb a
LEFT JOIN posts b
ON a.id = b.by_user
WHERE b.by_page = '0'
GROUP BY a.id,a.username

Answer 5

SELECT username, IFNULL(COUNT(b.by_user), 0) totalCount, IFNULL(SUM(c.votes), 0) total_votes
FROM users_fb a
LEFT JOIN posts b
ON a.id = b.by_user AND b.by_page = 0
LEFT JOIN posts c
ON a.id = b.by_user
GROUP BY username
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