mysql - 如何在 phpmyadmin 中加入表

Question

这是我需要合并的两个查询:

第一个查询:

SELECT emp.name, count(rej.employee_ic) as 'rejected leave'
FROM employee as emp
LEFT OUTER JOIN rejectedleave as rej
ON emp.ic_no = rej.employee_ic
GROUP BY emp.`ic_no`

第二个查询:

SELECT emp.name, count(app.employee_ic) as 'approved leave'
FROM employee as emp
LEFT OUTER JOIN approvedleave as app
ON emp.ic_no = app.employee_ic
GROUP BY emp.`ic_no`

输出:

第一个查询: first query output image

第二个查询: second query output image

我想将这两个表合并为一个表。请帮我解决这个问题，感谢您的帮助。

Answer 1

这是你需要的吗？它在单独的子查询中查找每个可用员工的批准和拒绝的休假计数，然后将其与员工表连接以在一行中显示每个员工的拒绝和批准的休假计数。

如果计数为空，则使用coalesce(col,0)返回0。 合并返回给定参数列表中的第一个非空值。

select
    t1.*,
    coalesce(t2.approvedleave,0) approvedleave
    coalesce(t3.rejectedleave,0) rejectedleave
from employee t1
left join (
    select employee_ic, count(*) approvedleave
    from approvedleave
    group by employee_ic
) t2 on t1.ic_no = t2.employee_ic
left join ( 
    select employee_ic, count(*) rejectedleave
    from rejectedleave
    group by employee_ic
) t3 on t1.ic_no = t3.employee_ic;

在这里阅读有关合并的内容:

• http://www.w3resource.com/mysql/comparision-functions-and-operators/coalesce-function.php