Postgres找到过渡

Question

我试图找到系统处于特定状态的所有时间段。状态登录到表中。数据的一个例子如下：

Time - State  
12:00 - 1  
12:01 - 1  
12:02 - 1  
12:03 - 1  
12:04 - 0  
12:05 - 0  
12:06 - 0  
12:07 - 1  
12:08 - 1

我希望看到的结果是：

Start - End - State  
12:00 - 12:03 - 1  
12:04 - 12:06 - 0  
12:07 - 12:08 - 1  

是否有任何预定义的功能来查找转换记录？

Answer 1

这样的事情应该有效：

SELECT "State",
       MIN("Time") AS Start,
       MAX("Time") AS End     
FROM (
  SELECT "Time", "State",
         ROW_NUMBER() OVER (ORDER BY "Time") - 
         ROW_NUMBER() OVER (PARTITION BY "State" ORDER BY "Time") AS grp
  FROM mytable) AS t
GROUP BY "State", grp  

内部查询使用标准技术来识别具有相同State值的连续记录的 islands 。外部查询使用计算列grp到GROUP BY并获取每个岛的Start，End值。