datediff带有选择条件的条件

Sql Server 2008 Datediff带有select语句中的条件。datediff带有选择条件的条件

我有下面的查询，需要帮助理解为什么我得到这些结果和我的问题的最佳解决方案。

SELECT DISTINCT l.program, l.id 
    ,(DATEDIFF(DAY, B.FIRST_DT , B.FIRST_second_DT))days_between1 
    ,(DATEDIFF(DAY, C.FIRST_DT , C.FIRST_second_DT))days_between2  
FROM l 
LEFT JOIN l B ON L.id = B.id AND L.SERVICE_DATE = B.SERVICE_DATE 
       AND B.FIRST_DT IS NOT NULL AND B.FIRST_DT IS NOT NULL 
       AND l.IS ='0' AND L.FIRST_V_DT IS NOT NULL 
LEFT JOIN l C ON L.id = C.id AND L.SERVICE_DATE = C.SERVICE_DATE 
       AND C.FIRST_DT IS NOT NULL 
       AND C.FIRST_A_DT IS NOT NULL AND L.IS ='1' 
       AND L.FIRST_DT IS NOT NULL 
WHERE 1=1

我得到两条线

Program id daysbetween1  daysbetween2 
blue  1  null    3 
blue  1   4    null

如何获取一条线，如下图所示，为什么我会收到两行呢？

Program id daysbetween1  daysbetween2 
blue  1  4    3

来源

2016-02-11 Mr John

示例数据将有助于此处。 http://stackoverflow.com/help/how-to-ask –

当然，你会得到不同的行，要么L.IS ='0'或L.IS ='1'... – jarlh

是要做我的L .IS = 0 AND L.IS = 1和我的内部联接。我将处理样本数据。 –

你可以试试这个方法：

SELECT l.program, l.id 
    ,MAX((DATEDIFF(DAY, B.FIRST_DT , B.FIRST_second_DT))) days_between1 
    ,MAX((DATEDIFF(DAY, C.FIRST_DT , C.FIRST_second_DT))) days_between2  
FROM l 
LEFT JOIN l B ON L.id = B.id AND L.SERVICE_DATE = B.SERVICE_DATE 
       AND B.FIRST_DT IS NOT NULL AND B.FIRST_DT IS NOT NULL 
       AND l.IS ='0' AND L.FIRST_V_DT IS NOT NULL 
LEFT JOIN l C ON L.id = C.id AND L.SERVICE_DATE = C.SERVICE_DATE 
       AND C.FIRST_DT IS NOT NULL 
       AND C.FIRST_A_DT IS NOT NULL AND L.IS ='1' 
       AND L.FIRST_DT IS NOT NULL 
GROUP BY l.program, l.id

这where条件是不必要的，除非你正在从某种过滤器的动态级联这个SQL。

来源

2016-02-11 18:04:34

datediff带有选择条件的条件

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