Question

Select
Max(isnull(UpdateDate, InsertDate)) as A
From yourTable
Where UpdateCode = 'ABC' or InsertCode = 'ABC'

Select
Max(isnull(UpdateDate, InsertDate)) as B
From yourTable
Where UpdateCode = 'ZYX' or InsertCode = 'ZYX'

我想在一个查询中进行这两个查询。所以我就这样做了

Select
Max(isnull(UpdateDate, InsertDate)) as A,
Max(isnull(UpdateDate, InsertDate)) as B
From yourTable
Where (UpdateCode = 'ZYX' or InsertCode = 'ZYX')
or (UpdateCode = 'ABC' or InsertCode = 'ABC')

此查询会带来错误的数据。

Answer 1

在您的查询中A和B是完全相同的字词，因此它们将具有完全相同的值。处理此问题的一种方法是在case调用中的max表达式中添加逻辑：

SELECT MAX(CASE WHEN 'ABC' IN (InsertCode, UpdateCode) 
                THEN ISNULL(UpdateDate, InsertDate)
           END) AS a
       MAX(CASE WHEN 'XYZ' IN (InsertCode, UpdateCode) 
                THEN ISNULL(UpdateDate, InsertDate)
           END) AS a
FROM  YourTable
-- Where clause is an optimization, functionality would be correct even without it
WHERE 'ABC' IN (InsertCode, UpdateCode) OR
      'XYZ' IN (InsertCode, UpdateCode)

Answer 2

我相信您想要有条件地计算每个MAX。

Select
    Max(CASE WHEN UpdateCode = 'ZYX' or InsertCode = 'ZYX' THEN isnull(UpdateDate, InsertDate) END) as A,
    Max(CASE WHEN UpdateCode = 'ABC' or InsertCode = 'ABC' THEN isnull(UpdateDate, InsertDate) END) as B
From 
    yourTable
Where   
    UpdateCode IN ('ZYX', 'ABC') or InsertCode IN ('ZYX', 'ABC')

Answer 3

一种非常简单的方法是将两个语句与“联盟选择”结合起来。

否则你必须清楚地描述你对结果的期望。

Answer 4

查询本身似乎有点奇怪，但我相信你有两个选择;

首先使用“IN”语句允许您的where条件能够满足多个条件

即

其次是使用JOIN来使两个字段匹配 - 我认为这更倾向于你的目标



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我需要一个帮助 - 改善这个糟糕的查询

4 个答案: