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：

姓名转移鲍勃史密斯4 简约翰逊2

我将非常感谢能得到的任何帮助。

Answer 1

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

您还可以使用LEFT JOIN编写查询：

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 ;

Answer 2

你可以尝试类似的东西

SELECT 
members.fname, 
members.lname, 
count(*) FROM duty_sched JOIN members
WHERE duty_sched.mbr_id = members.mbr_id
Group by duty_sched.mbr_id
ORDER BY members.lname, members.fname

Answer 3

试试这个：

SELECT m.fname, m.lname, IFNULL(A.shifts, 0) shifts
FROM members m 
LEFT JOIN (SELECT mbr_id, COUNT(id) shifts 
           FROM duty_sched GROUP BY mbr_id)  A ON m.mbr_id = A.mbr_id 
ORDER BY m.lname, m.fname;

MySQL左连接计数不起作用

3 个答案: