Question

我有这样的查询：

SELECT c.id, c.name, f.name
FROM companies c
INNER JOIN facilities f ON c.id = f.company
ORDER BY c.name DESC, f.name

我还想为每一行（每个设施）检索COUNT()（一个表）work_orders（一个包含0或1的列）的approved。

例如SELECT COUNT(*) FROM work_orders w WHERE w.facility = f.id AND w.approved = 1

结果应该是

company | facility | count
--------------------------
goog    | ohio     | 2
goog    | cali     | 0
tekk    | cupertin | 0

作为一种跟进，我还想添加另一个计数列w.approved = 0

Answer 1

SELECT c.id, c.name, f.name, COUNT(w.id) AS work_orders
FROM companies c
INNER JOIN facilities f ON c.id = f.company
-- LEFT JOIN used in case there are facilities with no work orders
LEFT JOIN work_orders w ON f.id = w.facility AND w.approved = 1
GROUP BY c.id, c.name, f.name
ORDER BY c.name DESC, f.name

进行多次计数（已批准或未批准）：

SELECT c.id, c.name, f.name, 
  wapp.wo AS approved_work_orders,
  wnapp.wo AS non_approved_work_orders,
FROM companies c
INNER JOIN facilities f ON c.id = f.company
LEFT JOIN (SELECT facility, COUNT(*) AS wo FROM work_orders WHERE approved=1 GROUP BY facility) wapp ON f.id = wapp.facility
LEFT JOIN (SELECT facility, COUNT(*) AS wo FROM work_orders WHERE approved=0 GROUP BY facility) wnapp ON f.id = wnapp.facility
ORDER BY c.name DESC, f.name

Answer 2

看起来你只需要对c.id和if语句进行分组

SELECT c.id, c.name, f.name, IF(count(0)>0,1,0) 
FROM companies c
INNER JOIN facilities f ON c.id = f.company
LEFT JOIN work_orders w ON w.facility = f.id
GROUP BY f.id
ORDER BY c.name DESC, f.name

计数和加入

2 个答案: