MySQL 算作一列

Question

我有如下表结构

leads
-id
-fname
-lname


subcontractors
-id
-leads_id
-fname
-lname
-status

潜在客户可以有多个分包商。 subcontractors.status 告诉分包商是活跃还是暂停

问题是如何选择带有计数列的潜在客户，该列显示他们有多少活跃和暂停的子客户？

我现在有这个:

SELECT 
l.id, 
l.fname, 
l.lname, 
s.status 
FROM leads l 
INNER JOIN subcontractors s 
ON l.id = s.leads_id 
GROUP BY l.id ORDER BY l.id DESC;

我的目标是拥有这样的东西

id | fname | lname | active_subcon_count | suspended_subcon_count 

Answer 1

您可以尝试使用条件聚合函数 COUNT 和 CASE WHEN

SELECT 
    l.id, 
    l.fname, 
    l.lname, 
    COUNT(CASE WHEN s.status = 'active' THEN 1 END) ,
    COUNT(CASE WHEN s.status = 'suspended' THEN 1 END) 
from leads l 
INNER JOIN subcontractors s 
ON l.id = s.leads_id 
GROUP BY l.id , l.fname, l.lname
ORDER BY l.id DESC;

或者 mysql 可以像这样执行 SUM。

SELECT 
    l.id, 
    l.fname, 
    l.lname, 
    SUM(s.status = 'active') active_subcon_count ,
    SUM(s.status = 'suspended') suspended_subcon_count 
from leads l 
INNER JOIN subcontractors s 
ON l.id = s.leads_id 
GROUP BY l.id , l.fname, l.lname
ORDER BY l.id DESC;