MySQL左连接计数不起作用

Question

我有2个表(成员,duty_sched)我希望能够计算每个成员在duty_sched表中出现的时间.这是我几周后搜索的内容

SELECT 
members.fname, 
members.lname, 
(SELECT COUNT(duty_sched.id) FROM duty_sched
 WHERE 'duty_sched.mbr_id' = 'members.mbr_id') AS shifts 

FROM members
ORDER BY members.lname, members.fname

我得到的输出都是零,我希望它给我看的是:

名字转移鲍勃史密斯4简约翰逊2

我将非常感谢您提供的任何帮助.

Answer 1

删除单引号: WHERE duty_sched.mbr_id = members.mbr_id)

您还可以使用以下命令编写查询LEFT JOIN:

SELECT 
    m.fname, 
    m.lname, 
    COUNT(d.id) AS shifts 
FROM members AS m
  LEFT JOIN duty_sched AS d
    ON d.mbr_id = m.mbr_id
GROUP BY
    m.mbr_id                     -- the Primary Key of `members`
ORDER BY 
    m.lname, m.fname ;