如何根据特定条件按 SQL 分组？

Question

我使用的是 Microsoft SQL Server 2014，我有以下关于看电视的人的数据：

这里的时间是从午夜算起的分钟数。

PersonId   StartTime  EndTime
1          300        600
1          250        700
1          200        800
1          900        1200
2          100        200

现在如你所见，我想得到的是第1个人的观看陈述分组如下：

250 - 700 与 300 - 600 重叠，所以我想做的是从开始时间开始取最小值，从结束时间取最大值，因为它们重叠，我想对第 1 个人的所有观看陈述都这样做.但是我怎样才能用一个分组来做到这一点呢？

谢谢

Answer 1

缺口和孤岛

DECLARE @TVWatchingTime TABLE (PersonId int, StartTime int, EndTime int)
INSERT INTO @TVWatchingTime 
VALUES 
(1,          300,        600),
(1,          250,        700),
(1,          200,        800),
(1,          900,        1200),
(2,          100,        200)

;WITH cteSource(PersonId, StartTime, EndTime)
AS 
(
    SELECT
        s.PersonId, s.StartTime, e.EndTime
    FROM        
    (
        SELECT  PersonId, StartTime, ROW_NUMBER() OVER (ORDER BY StartTime) AS rn
        FROM    @TVWatchingTime
    ) AS s
    INNER JOIN 
    (
        SELECT  PersonId, EndTime, ROW_NUMBER() OVER (ORDER BY EndTime) + 1 AS rn
        FROM    @TVWatchingTime
    ) AS e ON s.PersonId = e.PersonId AND e.rn = s.rn
    WHERE s.StartTime > e.EndTime

    UNION ALL

    SELECT PersonId, MIN(StartTime), MAX(EndTime)
    FROM    @TVWatchingTime
    GROUP BY PersonId
), cteGrouped(PersonId, theTime, grp)
AS (
    SELECT  PersonId, u.theTime,
        (ROW_NUMBER() OVER (ORDER BY u.theTime) - 1) / 2
    FROM    cteSource AS s
    UNPIVOT (
            theTime
            FOR theColumn IN (s.StartTime, s.EndTime)
        ) AS u
)
SELECT PersonId, MIN(theTime) StartTime, MAX(theTime) EndTime
FROM cteGrouped
GROUP BY PersonId, grp
ORDER BY PersonId, grp

Returns:

PersonId    StartTime   EndTime
1           200         800
1           900         1200
2           100         200

如何根据特定条件按 SQL 分组？

How to group by SQL based on certain conditions?

sql

sql-server

sql-server-2014