[英]MySQL GROUP_CONCAT and JOIN
媒體表:
CREATE TABLE $media_table (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(300) DEFAULT NULL,
`options` longtext DEFAULT NULL,
PRIMARY KEY (`id`)
}
表格示例:
id title options
--------------------------
1 video ...
2 video ...
3 audio ...
類別表:
CREATE TABLE $media_taxonomy_table (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`type` varchar(15) DEFAULT NULL,
`title` varchar(300) DEFAULT NULL,
`media_id` int(11) unsigned DEFAULT NULL,
PRIMARY KEY (`id`),
INDEX `media_id` (`media_id`)
}
類型可以是“類別”或“標簽”(我猜這可能是枚舉)
表格示例:
id type title media_id
---------------------------------------
1 category rock 1
2 category trance 1
3 category trance 2
4 category rock 3
5 tag silent 1
5 tag loud 1
6 tag foo 2
我正在嘗試對 $media_taxonomy_table 中的類別和標簽進行 GROUP_CONCAT。
此查詢將返回僅包含類別的 GROUP_CONCAT
SELECT mt.id, mt.title, mt.options, GROUP_CONCAT(mtt.title ORDER BY mtt.title ASC SEPARATOR ', ') as category
FROM $media_table as mt
LEFT JOIN $media_taxonomy_table as mtt
ON mt.id = mtt.media_id AND mtt.type='category'
WHERE playlist_id = %d
GROUP BY mt.id
結果,收到:
id title options category
----------------------------------------
1 video ... rock, trance
2 video ... trance
3 audio ... rock
預期(我也需要標簽):
id title options category tag
--------------------------------------------------------------
1 video ... rock, trance silent, load
2 video ... trance foo
3 audio ... rock
您可以進行條件聚合:
SELECT
mt.id,
mt.title,
mt.options,
GROUP_CONCAT(CASE WHEN mtt.type = 'category' THEN mtt.title END ORDER BY mtt.title SEPARATOR ', ') as categories,
GROUP_CONCAT(CASE WHEN mtt.type = 'tag' THEN mtt.title END ORDER BY mtt.title SEPARATOR ', ') as tags
FROM $media_table as mt
LEFT JOIN $media_taxonomy_table as mtt ON mt.id = mtt.media_id
WHERE mt.playlist_id = %d
GROUP BY mt.id, mt.title, mt.options
似乎你需要另一個 group_concat 所以你需要另一個加入
SELECT mt.id
, mt.title
, mt.options
, GROUP_CONCAT(mtt.title ORDER BY mtt.title ASC SEPARATOR ', ') as category
, GROUP_CONCAT(mtt2.title ORDER BY mtt.title ASC SEPARATOR ', ') as tag
FROM $media_table as mt
LEFT JOIN $media_taxonomy_table as mtt
ON mt.id = mtt.media_id AND mtt.type='category'
LEFT JOIN $media_taxonomy_table as mtt2
ON mt.id = mtt.media_id AND mtt.type='tag'
WHERE playlist_id = %d
GROUP BY mt.id
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