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mysql 组函数count的具体用法
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- 2016-06-06 09:45:551126parcourir
mysqlcount
SELECT d.department,
COUNT(CASE e.sex WHEN e.sex='f' AND p.position !='主管' THEN p.id END) fq,
COUNT(CASE e.sex WHEN e.sex='f' AND p.position ='主管' THEN p.id END) fz,
COUNT(CASE e.sex WHEN e.sex='m' AND p.position !='主管' THEN p.id END) mq,
COUNT(CASE e.sex WHEN e.sex='m' AND p.position ='主管' THEN p.id END) mz,
COUNT(e.id) xj
FROM department d LEFT JOIN employ e ON d.id=e.deptid
LEFT JOIN position p ON e.positionid=p.id
GROUP BY d.id;
出现后面两个count统计不出来是什么原因？
为什么下面个可以查出来？
SELECT d.department,
COUNT(CASE WHEN e.sex='f' AND p.position !='主管' THEN p.id END) fq,
COUNT(CASE WHEN e.sex='f' AND p.position ='主管' THEN p.id END) fz,
COUNT(CASE WHEN e.sex='m' THEN CASE WHEN p.position !='主管' THEN p.id END END) mq
COUNT(CASE WHEN e.sex='m' THEN CASE WHEN p.position ='主管' THEN p.id END END) mz,
COUNT(e.id) xj
FROM department d LEFT JOIN employ e ON d.id=e.deptid
LEFT JOIN position p ON e.positionid=p.id
GROUP BY d.id