Multiple GROUP BY and COUNT in MySQL - mysql

Question

My Sql structure :
CREATE TABLE collection (
id int(11) NOT NULL AUTO_INCREMENT,
user_id int(11) DEFAULT NULL,
`name` varchar(250) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (id),
KEY user_id (user_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
CREATE TABLE collection_link (
id bigint(20) NOT NULL AUTO_INCREMENT,
collection_id int(11) DEFAULT NULL,
configitem_id bigint(20) DEFAULT NULL,
PRIMARY KEY (id),
KEY IDX_7CDBB51F514956FD (collection_id),
KEY IDX_7CDBB51F9D3DD91F (configitem_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
CREATE TABLE configitem (
id bigint(20) NOT NULL,
PRIMARY KEY (id),
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
CREATE TABLE user_account (
id int(11) NOT NULL AUTO_INCREMENT,
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
ALTER TABLE collection
ADD CONSTRAINT FK_FC4D6532A76ED395 FOREIGN KEY (user_id) REFERENCES user_account (id),
ALTER TABLE collection_link
ADD CONSTRAINT FK_7CDBB51F514956FD FOREIGN KEY (collection_id) REFERENCES collection (id),
ADD CONSTRAINT FK_7CDBB51F9D3DD91F FOREIGN KEY (configitem_id) REFERENCES configitem (id);
Second, a user_account can add many configitems in collections and also can add the same items in collections as he want.
With that, I need to find the top configitems added in collections and avoid duplicate added by users in their collections. Aka if a user have 5 same configitems in one collection count only one... And that's my problem.
With that:
SELECT id, SUM(num) FROM (
SELECT l.configitem_id as id, COUNT(DISTINCT l.configitem_id) as num FROM collection_link l LEFT JOIN collection c9_ ON l.collection_id
= c9_.id LEFT JOIN user_account u2_ ON c9_.user_id = u2_.id WHERE l.configitem_id = 1121 GROUP BY u2_.id, l.configitem_id
) as cmpt;
I can receive the exact count for configitem 1121 but how to apply to all?
Because all my tests fail...
This works and takes top 25 added :
SELECT DISTINCT c2_.id AS id_0, count(c1_.id) AS sclr_1
FROM collection_link c1_
LEFT JOIN configitem c2_ ON c1_.configitem_id = c2_.id
LEFT JOIN collection c8_ ON c1_.collection_id = c8_.id
LEFT JOIN user_account u9_ ON c8_.user_id = u9_.id
GROUP BY c2_.id
ORDER BY sclr_1 DESC LIMIT 25;
but takes duplicates.

Answer 1

If I understand correctly, you need to aggregate by user and config item before taking the count. Or, simply do a count(distinct):
SELECT c2_.id AS id_0,
COUNT(DISTINCT u9_.id) AS sclr_1
FROM collection_link c1_ LEFT JOIN
configitem c2_
ON c1_.configitem_id = c2_.id LEFT JOIN
collection c8_
ON c1_.collection_id = c8_.id LEFT JOIN
user_account u9_
ON c8_.user_id = u9_.id
GROUP BY c2_.id
ORDER BY sclr_1 DESC
LIMIT 25;
Note that this version of the query does not need to join to the user table:
SELECT c2_.id AS id_0,
COUNT(DISTINCT c8_.user_id) AS sclr_1
FROM collection_link c1_ LEFT JOIN
configitem c2_
ON c1_.configitem_id = c2_.id LEFT JOIN
collection c8_
ON c1_.collection_id = c8_.id
GROUP BY c2_.id
ORDER BY sclr_1 DESC
LIMIT 25;