Question

我想根据两个日期时间是否共享来比较两个日期时间。这有效：

SELECT *
FROM XXX
WHERE CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE)

但是，我实际上希望将结果作为额外的一列：

SELECT 
    CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE)
    , *
FROM XXX

后者不起作用，因为SQLServer抱怨语法无效。有什么建议吗？

结果应如下：

LoadDateLAG | LoadDateLEAD | (LoadDateLAG = LoadDateLEAD) [as bit]

我需要此功能来压缩历史表 -删除不必要的条目（例如，每天仅保留最后一个条目）。

Answer 1

SQL Server 2012 +

SELECT IIF(CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE),1,0),* FROM XXX

Answer 2

您可以使用CASE WHEN：

SELECT
    LoadDateLAG, LoadDateLEAD,
    CASE WHEN CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE) THEN 1 ELSE 0 END AS isDateEquals
FROM XXX
-- WHERE CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE)

如果您还想显示DATE值（而不是DATETIME)，则可以使用以下SELECT：

 SELECT 
    CAST(LoadDateLAG AS DATE) AS LoadDateLAG,
    CAST(LoadDateLEAD AS DATE) AS LoadDateLEAD,
    CASE WHEN CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE) THEN 1 ELSE 0 END AS isDateEquals
FROM XXX
-- WHERE CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE)

如果要显示等于的DATE值（而不是1或0），则可以使用以下SELECT：

SELECT 
    LoadDateLAG, LoadDateLEAD,
    CASE WHEN CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE) THEN CAST(LoadDateLAG AS DATE) ELSE NULL END AS equalsDate
FROM XXX
-- WHERE CAST(LoadDateLAG AS DATE) = CAST(LoadDateLEAD AS DATE)

演示： http://sqlfiddle.com/#!18/30b0e/11/1

比较选择的日期时间和仅日期

2 个答案: