SQL查询以查找日期之间的差异的平均值 [英] SQL Query to find average of difference between dates

问题描述

我有一个列，其数据类似

I have a column that has data like

Date
13/8/2011
2/9/2011
10/9/2011
20/9/2011

我需要编写一个SQL查询/过程，这将帮助我得到日期之间的差异的平均值。
对于上面的例子，它将是（19 + 8 + 10）/3=12.33
请帮助这个。

I need to write a SQL query/procedure that will help me get the average of the differences between the dates. For the above example it would be (19+8+10)/3=12.33 Please help with this.

感谢Advance，
Geetha

Thanks in Advance, Geetha

推荐答案

我不知道你的RDBMS，但这是从SQL服务器。此外，您的一个计算机错误 - 02/09/2011 - 13/08/2011是20，而不是19。

I don't know your RDBMS, but this is from SQL Server. Also, one of your calcs is wrong - 02/09/2011 - 13/08/2011 is 20, not 19.

create table dates (
    myDate  date
)

insert into dates
values ({d '2011-08-13'}), 
    ({d '2011-09-02'}), 
    ({d '2011-09-10'}), 
    ({d '2011-09-20'})

;with orderedDates as (
    select ROW_NUMBER() OVER (order by myDate) as row, myDate
    from dates
), datediffs as (
    select DATEDIFF(dd, o2.myDate, o1.myDate) as diff
    from orderedDates o1 left outer join
        orderedDates o2 on o1.row = o2.row + 1
)
select AVG(cast(diff as decimal))
from datediffs
where diff is NOT NULL

结果生成是12.667：（20 + 8 + 10）/ 3。

Result produced is 12.667: (20 + 8 + 10)/3.

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