如何计算连续日期

Question

例如,有一些日期表:

2015-01-01
2015-01-02
2015-01-03
2015-01-06
2015-01-07
2015-01-11

我必须编写ms sql查询,它将返回从表中每个日期开始的连续日期的计数.结果如下:

2015-01-01   1
2015-01-02   2
2015-01-03   3
2015-01-06   1
2015-01-07   2
2015-01-11   1

在我看来,我应该使用LAG和LEAD功能,但现在我甚至无法想象思维方式.

Answer 1

CREATE TABLE #T ( MyDate DATE) ;
INSERT #T VALUES ('2015-01-01'),('2015-01-02'),('2015-01-03'),('2015-01-06'),('2015-01-07'),('2015-01-11')

SELECT 
    RW=ROW_NUMBER() OVER( PARTITION BY GRP  ORDER BY MyDate) ,MyDate
FROM
(
SELECT 
    MyDate, DATEDIFF(Day, '1900-01-01' , MyDate)- ROW_NUMBER() OVER( ORDER BY MyDate ) AS GRP
FROM #T 
) A

DROP TABLE #T;