Question

我需要以下解决方案

Group  Begindate enddate     
a1       1/1/2019   2/1/2019 
a1       2/1/2019   3/1/2019
a2       3/1/2019   3/2/2019
a2       3/2/2019   3/4/2019
a1       3/4/2019   3/5/2019
a1       3/5/2019   4/1/2019

在上面，我需要根据发生情况将其分为三个组。首先出现a1，然后出现a2，再出现a1。我的结果应该是这样的：

group  min(begindate)
a1      1/1/2019
a2       3/1/2019
a1       3/4/2019

感谢您的帮助。

Answer 1

这是一个gaps and islands问题。

SELECT group_id,MIN(begindate)
FROM ( SELECT t.*,ROW_NUMBER() OVER( order BY begindate
       ) - ROW_NUMBER() OVER(
            PARTITION BY group_id
            ORDER BY begindate
       ) AS seq
       FROM t
     )
GROUP BY group_id,seq
ORDER BY 2

DEMO

Oracle分组不止一次发生

1 个答案: