mysql - 如何编写查询来计算另一个表中没有外键的特定记录数？

Question

下面是我的Db的er图 我想从表 Subscription 中获取给定 Subscription.ClientId 的所有结果，每个 Subscription.RouteId 的 Assigned.ScreenId 的数量为该 Subscription.ClientId。我试过下面的代码，我也试过调整关系但没有成功，我怎么能在 yii 中做到这一点。

SELECT S. * , (

SELECT COUNT( C.ScreenId ) 
FROM (

SELECT B.ScreenId, A.RouteId, B.clientId
FROM Screens AS A
INNER JOIN Assigned AS B ON A.ScreenId = B.ScreenId
) AS C
WHERE S.RouteId = C.RouteId
) AS couNTER
FROM Subscription AS S
LIMIT 0 , 30

这是示例 http://sqlfiddle.com/#!2/38f2e7 的链接[注意:我删除了表格 subscribedscreens]

我想要的输出是

RouteId ClientId NumScreen NumAds... (Count(assignedScreenid)for given route)
1        1                              2
2        1                              1
1        2                              1
2        2                              3

Answer 1

试试下面的 sql，如果结果不是您想要的结果，那么也许可以澄清您期望的结果。

-- SELECT subscription.SubscriptionId, client.clientId, assigned.ScreenId, route.RouteId
SELECT route.RouteId, client.clientId, COUNT(assigned.ScreenId)
FROM subscription
  LEFT JOIN client ON client.ClientId = subscription.ClientId
  LEFT JOIN assigned ON assigned.ClientId = client.ClientId
  LEFT JOIN route ON route.RouteId = subscription.RouteId
GROUP BY assigned.ScreenId

结果:

ROUTEID   CLIENTID   COUNT(ASSIGNED.SCREENID)
   2         1         4
   2         1         2
   2         1         6
   1         2         2