How can I optimize this query? If you need the table structure just let me know, but this is being done as a custom plugin for Vanilla forums
SELECT
G.*
FROM
(
SELECT
D.DiscussionID,
A. NAME AS Category,
D. NAME,
U. NAME AS USER,
D.CountComments,
IFNULL(
MAX(C.DateInserted),
D.DateInserted
) AS Updated
FROM
GDN_Discussion AS D
LEFT OUTER JOIN GDN_Comment AS C ON D.DiscussionID = C.DiscussionID
INNER JOIN GDN_Category AS A ON A.CategoryID = D.CategoryID
LEFT OUTER JOIN GDN_User AS U ON U.UserID = D.InsertUserID
WHERE
A.CategoryID = '626'
GROUP BY
D.DiscussionID
) AS G
ORDER BY
G.Updated DESC
LIMIT 0, 10
Related
I have the following query in MySQL:
(SELECT ue.id, ue.userid, ue.status, ue.timestart, ue.timeend, e.courseid,
e.id AS enrolid, ra.roleid
FROM user_enrolments ue
JOIN enrol e ON e.id = ue.enrolid
JOIN course c ON c.id = e.courseid
JOIN user u ON u.id = ue.userid
JOIN context ct ON ct.instanceid = c.id
LEFT JOIN role_assignments ra ON ra.userid = u.id AND
ra.contextid = ct.id AND
ra.itemid = e.id
WHERE e.customint1 = 1 AND u.deleted = 0 AND
ct.contextlevel = 50 AND (ue.status = 0 OR ue.status = 1))
UNION
(SELECT de.enrolid AS id, de.userid, de.status, de.date_ini, de.date_fin,
de.courseid, de.enrolid, de.roleid
FROM deleted_enrols de
JOIN user u ON u.id = de.userid
WHERE userid = ANY (SELECT userid FROM local_users WHERE clientid = 1))
ORDER BY u.firstname, u.lastname, c.fullname LIMIT 0, 100
If I delete ORBER BY and LIMIT, this query works fine... but the ORDER BY clause gives an error:
Table 'u' from one of the SELECTs cannot be used in global ORDER clause
If I delete the parentheses of both SELECT querys, the error is different:
Table 'u' from one of the SELECTs cannot be used in field list
I have also tried with UNION ALL, but it does not work either.
Any suggestion or clue? Thanks in advance for your time...
The results of your UNION do not include any fields from table 'u', so those results cannot be sorted by table 'u' fields.
You could perhaps perform the UNION and then re-join the results to table 'u', and then use that to sort the results by table 'u' fields. A similar issue exists for sorting on
course.fullname, so that would need to be joined back in, too.
SELECT x.id, x.userid, x.status, x.timestart, x.timeend, x.courseid, x.enrolid, x.roleid
FROM ((SELECT ue.id, ue.userid, ue.status, ue.timestart, ue.timeend, e.courseid,
e.id AS enrolid, ra.roleid
FROM user_enrolments ue
JOIN enrol e ON e.id = ue.enrolid
JOIN course c ON c.id = e.courseid
JOIN user u ON u.id = ue.userid
JOIN context ct ON ct.instanceid = c.id
LEFT JOIN role_assignments ra ON ra.userid = u.id
AND ra.contextid = ct.id
AND ra.itemid = e.id
WHERE e.customint1 = 1 AND u.deleted = 0
AND ct.contextlevel = 50 AND (ue.status = 0 OR ue.status = 1))
UNION
(SELECT de.enrolid AS id, de.userid, de.status, de.date_ini, de.date_fin,
de.courseid, de.enrolid, de.roleid
FROM deleted_enrols de
JOIN user u ON u.id = de.userid
WHERE userid = ANY (SELECT userid FROM local_users WHERE clientid = 1))
) x
JOIN user z ON z.id = x.userid
JOIN course d ON d.id = x.courseid
ORDER BY z.firstname, z.lastname, d.fullname LIMIT 0, 100
Assuming you want to sort the whole lot, try parentheses round the whole query with the ORDER BY done afterwards:
select id, userid, status, timestart, timeend, courseid, enrolid, roleid from
((SELECT ue.id, ue.userid, ue.status, ue.timestart, ue.timeend, e.courseid,
e.id AS enrolid, ra.roleid, u.firstname, u.lastname, c.fullname
FROM user_enrolments ue
JOIN enrol e ON e.id = ue.enrolid
JOIN course c ON c.id = e.courseid
JOIN user u ON u.id = ue.userid
JOIN context ct ON ct.instanceid = c.id
LEFT JOIN role_assignments ra ON ra.userid = u.id AND
ra.contextid = ct.id AND
ra.itemid = e.id
WHERE e.customint1 = 1 AND u.deleted = 0 AND
ct.contextlevel = 50 AND (ue.status = 0 OR ue.status = 1))
UNION
(SELECT de.enrolid AS id, de.userid, de.status, de.date_ini, de.date_fin,
de.courseid, de.enrolid, de.roleid, u.firstname, u.lastname, ' ' as fullname
FROM deleted_enrols de
JOIN user u ON u.id = de.userid
WHERE userid = ANY (SELECT userid FROM local_users WHERE clientid = 1))) s1
ORDER BY firstname, lastname, fullname LIMIT 0, 100
(obviously fullname in the second SELECT statement would be populated however seems sensible)
You need to include the data to be ordered by in the selects of the unioned queries; an ORDER BY following a UNION is handled as if it were SELECT * FROM (unions) ORDER BY ... so anything not coming out of the union cannot be used for ordering.
Ironically, a query similar to that is the key to getting what you want though, with something like
SELECT x, y, z
FROM (
SELECT x, y, z, somethingIdontactuallywant
FROM blah
UNION
SELECT a, b, c, somethingIdontactuallywant
FROM blah2
) AS u
ORDER BY u.somethingIdontactuallywant
As mysql documentation on union says:
This kind of ORDER BY cannot use column references that include a
table name (that is, names in tbl_name.col_name format). Instead,
provide a column alias in the first SELECT statement and refer to the
alias in the ORDER BY. (Alternatively, refer to the column in the
ORDER BY using its column position. However, use of column positions
is deprecated.)
Also, if a column to be sorted is aliased, the ORDER BY clause must
refer to the alias, not the column name.
So, do not refer to any table names and use columns that are actually in the resultset of the union.
I have a query with one LEFT JOIN that works fine. When I add a second LEFT JOIN to a table with multiple records per field in the first table, however, I am getting the product of the results in the two tables ie books x publishers returned. How can I prevent this from happening?
SELECT a.*,b.*,p.*, group_concat(b.id as `bids`)
FROM authors `a`
LEFT JOIN books `b`
ON b.authorid = a.id
LEFT JOIN publishers `p`
on p.authorid = a.id
GROUP by a.id
EDIT:
Figured it out. The way to do this is to use subqueries as in this answer:
SELECT u.id
, u.account_balance
, g.grocery_visits
, f.fishmarket_visits
FROM users u
LEFT JOIN (
SELECT user_id, count(*) AS grocery_visits
FROM grocery
GROUP BY user_id
) g ON g.user_id = u.id
LEFT JOIN (
SELECT user_id, count(*) AS fishmarket_visits
FROM fishmarket
GROUP BY user_id
) f ON f.user_id = u.id
ORDER BY u.id;
If you do multiple LEFT Joins, your query will return a cartesian product of the results. To avoid this and get only one copy of fields you desire, do a subquery for each table you wish to join as below. Hope this helps someone in the future.
SELECT u.id
, u.account_balance
, g.grocery_visits
, f.fishmarket_visits
FROM users u
LEFT JOIN (
SELECT user_id, count(*) AS grocery_visits
FROM grocery
GROUP BY user_id
) g ON g.user_id = u.id
LEFT JOIN (
SELECT user_id, count(*) AS fishmarket_visits
FROM fishmarket
GROUP BY user_id
) f ON f.user_id = u.id
ORDER BY u.id;
I have this query in SQL that I KNOW it is horribly written. Could you guys help me write it in a decent, normal person manner?
Thanks.
select distinct R.*, X.LIKED
from Recipe R
left join (select distinct R.* , '1' as LIKED
from Recipe R, Likes L
where R.id = L.idRecipe
and L.email = 'dvader#deathstar.galacticempire') X
on R.id = X.id
looks like you need all from recipe with marks on liked by vader#deathstar.galacticempire
select R.*, likedR.LIKED
from Recipe R
left join (select distinct R.id , '1' as LIKED
from Recipe R
inner join Likes L on R.id = L.idRecipe
where
L.email = 'dvader#deathstar.galacticempire') likedR
on R.id = likedR.id
Thanks everyone for your help.
I was able to do what i wanted with this query:
select distinct R.*, X.LIKED, U.imgUrl
from User U, Recipe R
left join
(select distinct R.* , '1' as LIKED
from Recipe R, Likes L
where R.id = L.idRecipe and L.email = 'dvader#deathstar.ge') X
on R.id = X.id
where R.email = U.email
This will bring all the info i need in one table plus 1 extra column with either a 1 or a null if the entry of dvader is in another table, Using joins.
I have a fairly complicated SQL statement I am working on. Here is where I am at:
SELECT c.category
FROM master_cat as c
LEFT JOIN
(
SELECT cat_id, user_id COUNT(cat_id) favoriteCat
FROM ratings
GROUP BY user_id
) a ON a.cat_id= c.cat_id
LEFT JOIN users AS u
ON u.user_id AND a.user_id
WHERE u.username = '{$user}' LIMIT 1
This statement is incomplete. I am missing a middle table here. cat_id is not actually in ratings. But items_id is from a table called items and cat_id is also in that table as well.
So what I am trying to do is this:
SELECT rating FROM ??? GROUP BY cat_id where u.user=$user
The only thing I can think of doing maybe is another LEFT join with items inside favoriteCat but I am not sure if that is allowed.
I was overthinking this, here is my final solution:
SELECT c.category, count(r.rating) AS totalCount
FROM ratings as r
LEFT JOIN items AS i
ON i.items_id = r.item_id
LEFT JOIN users AS u
ON u.user_id = r.user_id
LEFT JOIN master_cat AS c
ON c.cat_id = i.cat_id
WHERE r.user_id = '{$user_id}'
GROUP BY c.category
ORDER BY totalCount DESC
Just wondering what's a better way to write this query. Cheers.
SELECT r.user_id AS ID, m.prenom, m.nom
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_user` AS m ON r.user_id = m.id
WHERE r.section_id = $section_id
AND l.rank = '$rank_name' AND depart_id IN
(SELECT depart_id FROM 0_depart WHERE user_id = $user_id AND section_id = $section_id)
GROUP BY r.user_id
Here are the table structures:
0_rank: id | section_id | rank_name |
other_stuffs
0_user: id | prenom | nom | other_stuffs
0_right: id | section_id | user_id |
rank_id | other_stuffs
0_depart: id | section_id | user_id | depart_id
| other_stuffs
The idea is to use the same in a function like:
public function usergroup($section_id,$rank_name,$user_id) {
// mysql query goes here to get a list of appropriate users
}
Update: I think I have not been able to express myself clearly earlier. Here is the most recent query that seems to be working.
SELECT m.id, m.prenom, m.nom,
CAST( GROUP_CONCAT( DISTINCT d.depart ) AS char ) AS deps,
CAST( GROUP_CONCAT( DISTINCT x.depart ) AS char ) AS depx
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
LEFT JOIN `0_depart` AS d ON m.id = d.user_id
LEFT JOIN `0_depart` AS x ON x.user_id = $user_id
WHERE r.section = $section_id
AND l.rank = '$rank_name'
GROUP BY r.user_id ORDER BY prenom, nom
Now I want to get only those result, where all entries of deps are present in entries in depx.
In other term, every user is associated with some departs. $user_id is also an user is associated with some departs.
I want to get those users whose departs are common to the departs of $user_id.
Cheers.
Update
I'm not sure without being able to see the data but I believe this query will give you the results you want the fastest.
SELECT m.id, m.prenom, m.nom,
CAST( GROUP_CONCAT( DISTINCT d.depart ) AS char ) AS deps,
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id and r.user_id = $user_id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
LEFT JOIN `0_depart` AS d ON m.id = d.user_id
WHERE r.section = $section_id
AND l.rank = '$rank_name'
GROUP BY r.user_id ORDER BY prenom, nom
Let me know if this works.
Try this:
(By converting the functionality of the IN (SELECT...) to an inner join, you get exactly the same results but it might be the optimizer will make better choices.)
SELECT r.user_id AS ID, m.prenom, m.nom
FROM `0_rank` AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id and r.section_id = 2
LEFT JOIN `0_user` AS m ON r.user_id = m.id
INNER JOIN `0_depart` AS x ON l.section_id = x.section_id and x.user_id = $user_id AND x.section_id = $section_id
WHERE l.rank = 'mod'
GROUP BY r.user_id
I also moved the constraints on 0_right to the join statement because I think that is clearer -- presumably this change won't matter to the optimizer.
I know nothing about your DB structure but your subselect looks like it can be replaced with a simple INNER JOIN against whatever table has the depart column. MySQL is well known for its poor subquery optimization.
Without knowing the structures or indexes, I would first add "STRAIGHT_JOIN" if the critical criteria is in-fact from the 0-rank table. Then, ensure 0_rank has an index on "rank". Next, ensure the 0_right has an index on rank_id at a minimum, but rank_id, section to take advantage of BOTH your criteria. Index on 0_member on id.
Additionally, do you mean left-join (ie: record only required in the 0_rank or 0_member) on the respective 0_right and 0_member tables instead of a normal join (where BOTH tables must match on their IDs).
Finally, ensure index on the depart table on user_id.
SELECT STRAIGHT_JOIN
r.user_id AS ID,
m.prenom,
m.nom
FROM
0_rank AS l
LEFT JOIN `0_right` AS r
ON l.id = r.rank_id
AND r.section = 2
LEFT JOIN `0_member` AS m
ON r.user_id = m.id
WHERE
l.rank = 'mod'
AND depart IN (SELECT depart
FROM 0_depart
WHERE user_id = 2
AND user_sec = 2)
GROUP BY
r.user_id
---- revised post from feedback.
From the parameters you are listing, you are always including the User ID... If so, I would completely restructure it to get whatever info is for that user. Each user should apparently can be associated to multiple departments and may or may NOT match the given rank / department / section you are looking for... I would START the query with the ONE USER because THAT will guarantee a single entry, THEN tune-down to the other elements...
select STRAIGHT_JOIN
u.id,
u.prenom,
u.nom,
u.other_stuffs,
rank.rank_name
from
0_user u
left join 0_right r
on u.id = r.user_id
AND r.section_id = $section_id
join 0_rank rank
on r.rank_id = rank.id
AND rank.rank_name = '$rank_name'
left join 0_dept dept
on u.id = dept.user_id
where
u.id = $user_id
Additionally, I have concern about your table relationships and don't see a legit join to the department table...
0_user
0_right by User_ID
0_rank by right.rank_id
0_dept has section which could join to rank or right, but nothing to user_id directly
Run explain on the query - it will help you find where the caveats are:
EXPLAIN SELECT r.user_id AS ID, m.prenom, m.nom
FROM 0_rank AS l
LEFT JOIN `0_right` AS r ON r.rank_id = l.id
LEFT JOIN `0_member` AS m ON r.user_id = m.id
WHERE r.section = 2
AND l.rank = 'mod' AND depart IN
(SELECT depart FROM 0_depart WHERE user_id = 2 AND user_sec = 2)
GROUP BY r.user_id\G