在嵌套 SELECTS 中使用 COUNT

Question

我正在尝试计算某列中某个值的实例数，return 它在另一列中的实例数。我已经使用硬编码值成功完成了计算，但无法弄清楚如何从主 SELECT 获取变量到 COUNT。

在底部的示例数据中，CommissionRate 显示该行中的 DealInstanceOID 值出现在 DealInstanceOID 列中的次数。我的硬编码解决方案适用于所有这些值，但让它动态发生让我感到困惑。 DealInstanceOID 变量超出了嵌套 SELECT 的范围，我不确定如何解决这个问题。

我之前发布了这个问题，并且对我的表的连接方式有一些抱怨 - 无法从这些发布者那里获得更多反馈，我正在按照他们的建议重新发布。

SELECT
D.DealOID
DD.DealInstanceOID
, CommissionRate = (SELECT (DealInstanceOID COUNT(*) FROM dbo.DealDetail WHERE DealInstanceOID = 4530))
, Commission = CONVERT(MONEY,C.Commission,1)

FROM dbo.Book AS B WITH(NOLOCK)
INNER JOIN Contract as C WITH(NOLOCK) ON B.BookOID = C.BookOID
INNER JOIN Deal as D WITH(NOLOCK)ON C.ContractOID = D.ContractOID
INNER JOIN DealInstance DI WITH(NOLOCK) ON DI.DealOID = D.DealOID
INNER JOIN DealDetail AS DD WITH(NOLOCK)ON DD.DealInstanceOID = DI.DealInstanceOID

GROUP BY
DD.DealInstanceOID
, D.DealOID 
, C.Commission
, B.BookOID

ORDER BY DealOID ASC


DealOID |Commission |CommissionRate|Commission/Rate|DealInstanceOID
101     |  00    |       5      |     0.00   |     4530
101     |  00    |       5      |     0.00   |     4530
101     |  00    |       5      |     0.00   |     4530
101     |  00    |       5      |     0.00   |     4530
101     |  00    |       5      |     0.00   |     4530
101     |  00    |       6      |     3.33   |     4531
102     |  00    |       6      |     3.33   |     4531
102     |  00    |       6      |     3.33   |     4531
102     |  00    |       6      |     3.33   |     4531
102     |  00    |       6      |     3.33   |     4531
102     |  00    |       6      |     3.33   |     4531
103     |  00    |       3      |     ,000.00 |     4540
103     |  00    |       3      |     ,000.00 |     4540
103     |  00    |       3      |     ,000.00 |     4540

Answer 1

您应该可以通过 table 别名和列名称引用它：

...
 WHERE dbo.DealDetail.DealInstanceOID = DD.DealInstanceOID))
...

Answer 2

标量子select 语句有两个问题。一个是语法错误，另一个是引用。按如下方式修复它们：

CommissionRate = (SELECT COUNT(*) FROM dbo.DealDetail as s WHERE s.DealInstanceOID = dd.DealInstanceOID)

Answer 3

对每一行使用联接而不是 select。

关键是使用 CTE。正如您在下面看到的，结果是针对数据库的两个 select，而不是每行一个。

WITH counts AS
(  -- This will give a virtual table (CTE) with ID and count
   SELECT DealInstanceOID, COUNT(*) as C
   FROM dbo.DealDetail
   GROUP BY DealInstanceOID
)
SELECT
  D.DealOID,
  DI.DealInstanceOID,
  counts.C AS CommissionRate,
  CONVERT(MONEY,C.Commission,1) AS Commission 
FROM dbo.Book AS B WITH(NOLOCK)
JOIN Contract as C WITH(NOLOCK) ON B.BookOID = C.BookOID
JOIN Deal as D WITH(NOLOCK)ON C.ContractOID = D.ContractOID
JOIN DealInstance DI WITH(NOLOCK) ON DI.DealOID = D.DealOID
JOIN counts ON DI.DealInstanceOID = counts.DealInstanceOID
GROUP BY DI.DealInstanceOID, D.DealOID, C.Commission, B.BookOID
ORDER BY DealOID ASC

在嵌套 SELECTS 中使用 COUNT

Using COUNT in nested SELECTS

sql

sql-server

count