报告存储过程 - 如何避免重复？答案

【问题标题】：Reporting Stored Procedure - How to avoid duplication?报告存储过程 - 如何避免重复？
【发布时间】：2010-01-26 18:29:28
【问题描述】：

我正在编写一个报告存储过程。我想获取未确认和未开票的采购订单的数量，并能够（可选）过滤CustomerID。

我下面的内容按预期工作，但我担心 a) 它很慢 b) WHERE 子句的 CustomerID 部分存在重复。

你会如何编写这个存储过程，Stack Overflow？

SELECT 
  (SELECT COUNT(*)
   FROM PurchaseOrder
   WHERE AcknowledgmentStatus <> 'Complete'
   AND (@CustID = 0 OR CustomerID = @CustID)
  ) AS NonAckd,
  (SELECT COUNT(*)
   FROM PurchaseOrder
   WHERE InvoiceStatus <> 'Complete'
   AND (@CustID = 0 OR CustomerID = @CustID)
  ) AS NonInvoiced

【问题讨论】：

标签： sql sql-server stored-procedures refactoring query-optimization

【解决方案1】：

类似这样的：

SELECT Sum(Case When AcknowledgmentStatus <> 'Complete' Then 1 ELSE 0 END) as NonAckd
      ,Sum(Case When InvoiceStatus <> 'Complete'        Then 1 ELSE 0 END) as NonInvoiced 
  FROM PurchaseOrder 
 WHERE CustomerID = IsNull(NullIf(@CustID, 0), CustomerID)

【讨论】：

这正是我一直在寻找的东西！我不敢相信我从未见过CASE WHEN 结构。

【解决方案2】：

我不确定 100% 你在追求什么，但你可以将客户部分简化如下：（未经 [tired] memory 测试）

set @custID = nullif(@custID,0)

SELECT 
  (SELECT COUNT(*)
   FROM PurchaseOrder
   WHERE AcknowledgmentStatus <> 'Complete'
   AND ( CustomerID = isnull(@CustID,CustomerID) )
  ) AS NonAckd,
  (SELECT COUNT(*)
   FROM PurchaseOrder
   WHERE InvoiceStatus <> 'Complete'
   AND ( CustomerID = isnull(@CustID,CustomerID) )
  ) AS NonInvoiced

【讨论】：

【解决方案3】：

你不能使用：

COUNT 因为它会计算所有行（1 或 0 不为空，所以它会计算它们）
COUNT DISTINCT 将给出 2（仅值 1 和 0）

如果您删除状态检查，如果您可以处理零，它当然会运行得更快。

SELECT
    CASE WHEN AcknowledgmentStatus <> 'Complete' THEN 1 ELSE 0 END AS NonAckd,
    CASE WHEN InvoiceStatus <> 'Complete' THEN 1 ELSE 0 END AS NonInvoiced,
FROM
    PurchaseOrder
WHERE
    (AcknowledgmentStatus <> 'Complete' OR  InvoiceStatus <> 'Complete') --optional
    AND
    (@CustID = 0 OR CustomerID = @CustID)

【讨论】：