sql - SQL 中合并相邻行？

Question

我正在根据员工的工作时间段进行一些报告。在某些情况下，数据包含两个单独的记录，实际上是一个时间 block 。

这是该表的基本版本和一些示例记录:

EmployeeID
StartTime
EndTime

数据:

EmpID      Start         End
----------------------------
#1001   10:00 AM    12:00 PM
#1001    4:00 PM     5:30 PM
#1001    5:30 PM     8:00 PM

在该示例中，最后两条记录在时间上是连续的。我想编写一个组合任何相邻记录的查询，因此结果集如下:

EmpID      Start         End
----------------------------
#1001   10:00 AM    12:00 PM
#1001    4:00 PM     8:00 PM

理想情况下，它还应该能够处理 2 个以上的相邻记录，但这不是必需的。

Answer 1

本文为您的问题提供了多种可能的解决方案

http://www.sqlmag.com/blog/puzzled-by-t-sql-blog-15/tsql/solutions-to-packing-date-and-time-intervals-puzzle-136851

这似乎是最直接的:

WITH StartTimes AS
(
  SELECT DISTINCT username, starttime
  FROM dbo.Sessions AS S1
  WHERE NOT EXISTS
    (SELECT * FROM dbo.Sessions AS S2
     WHERE S2.username = S1.username
       AND S2.starttime < S1.starttime
       AND S2.endtime >= S1.starttime)
),
EndTimes AS
(
  SELECT DISTINCT username, endtime
  FROM dbo.Sessions AS S1
  WHERE NOT EXISTS
    (SELECT * FROM dbo.Sessions AS S2
     WHERE S2.username = S1.username
       AND S2.endtime > S1.endtime
       AND S2.starttime <= S1.endtime)
)
SELECT username, starttime,
  (SELECT MIN(endtime) FROM EndTimes AS E
   WHERE E.username = S.username
     AND endtime >= starttime) AS endtime
FROM StartTimes AS S;