有人能解释一下为什么group by子查询的添加使得这个查询花费了这么长的时间(30秒):FROM aggregate_songlist AS aON a.musical_work_id = m.id(SELECT sources.musical_work_id FROM sources GROUP BY sources.musical_work_id HAVING COUNT(sources.musical_work
我正在尝试生成一个列表的所有用户的标签与他们关联的任务数量的计数… SELECT * FROM count(task_tags.tag_id) AS TaskCount LEFT JOIN task_tags ON tags.tag_id = task_tags.tag_id GROUP BY tag_id )
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