我有两个表 i) team ii) team_member。 team_member 表包含每个团队下的所有成员。
团队表看起来像这样:
+-----------------------+ | team | |-----------------------| | id | name | status | |-----------------------| | 1 | Team 1 | Active | |-----------------------| | 2 | Team 2 | Active | |-----------------------| | 3 | Team 3 | Active | |-----------------------| | 4 | Team 4 |Inactive| |-----------------------| | 5 | Team 5 | Active | +-----------------------+
Team Member Table look like this :
+--------------------------------------+ | team_member | |--------------------------------------| |tm_id| team_id | user_id | status | |--------------------------------------| | 1 | 1 | 2 | Inactive | |--------------------------------------| | 2 | 1 | 2 | Active | |--------------------------------------| | 3 | 1 | 3 | Active | |--------------------------------------| | 4 | 2 | 4 | Active | |--------------------------------------| | 5 | 2 | 5 | Inactive | +--------------------------------------+
What result I'm expecting is this :
+------------------+ | expected result | |------------------| | id | count | |------------------| | 1 | 2 | |------------------| | 2 | 1 | |------------------| | 3 | 0 | |------------------| | 5 | 0 | +------------------+
It is basically number of all active member under each group of the team.
My SQL query is this :
SELECT team.id, COUNT( team_member.tm_id )
FROM `team`
LEFT JOIN team_member ON team_member.team_id = team.id
AND team_member.status = 'Active'
GROUP BY team_member.team_id
现在出现的问题是 SQL 查询部分工作。如果每个团队至少有一名成员，则查询工作正常。如果它找到一个没有成员的组，那么它会将其添加到结果中，但之后停止。
如果 team_member 表为空，我得到的结果是:
+------------------+ | expected result | |------------------| | id | count | |------------------| | 1 | 0 | +------------------+
任何人都可以在查询错误的地方停下来吗？应该是正确的查询。
谢谢。
最佳答案
按 team.id 而不是 team_member.team_id 对数据进行分组，因为 team_member 表不包含所有团队 ID。
试试这个:
SELECT team.id, COUNT( team_member.tm_id )
FROM `team`
LEFT JOIN team_member ON team_member.team_id = team.id
AND team_member.status = 'Active'
GROUP BY team.id;
SQL Fiddle 示例:http://sqlfiddle.com/#!9/65a397/2
关于mysql - 如何从右侧表中加入每组的行数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36232402/