按行之间的差异对 SQL 进行分组？

Question

我正在取几个数据点的最小值和最大值，但其中一些数据点让患者在不同的日子前往相同的地点。 有没有办法添加一个索引或代码，根据 order by 语句或类似的东西将它们区分为单独的组？ 我想将它们区分为单独的组（通过分离患者离开一个位置，去了一个新的位置，然后返回到原来的位置（在分组方面将其视为一个新位置）？

这是制作虚拟数据表的代码。

    CREATE TABLE #StartandStop (
     [hospitalname] varchar(255),
     pt_id varchar(255),
     [Location] varchar(255),
     startdatetime datetime,
     enddatetime datetime
     ); 

     INSERT INTO #StartandStop ([hospitalname],[pt_id],[Location],[startdatetime],[enddatetime])
     VALUES ('ClevelandClinic', '1','A','01-01-2020 10:35', '01-02-2020 12:30'),
     ('ClevelandClinic', '1','B','01-02-2020 12:30', '01-03-2020 00:00'),
     ('ClevelandClinic', '1','B','01-03-2020 00:00', '01-04-2020 00:00'),
     ('ClevelandClinic', '1','B','01-04-2020 00:00', '01-04-2020 19:30'),
     ('ClevelandClinic', '1','C','01-04-2020 19:30', '01-05-2020 18:44'),
     ('ClevelandClinic', '1','B','01-05-2020 18:44', '01-05-2020 07:09'),
     ('ClevelandClinic', '1','D','01-05-2020 07:09', '01-05-2020 22:22'),
     ('ClevelandClinic', '1','D','01-05-2020 22:22', '01-06-2020 00:00'),
     ('ClevelandClinic', '1','D','01-06-2020 00:00', '01-07-2020 00:00'),
     ('ClevelandClinic', '1','D','01-07-2020 00:00', '01-08-2020 00:00'),
     ('ClevelandClinic', '1','C','01-08-2020 00:00', '01-08-2020 20:02');

这是获得结果的代码。

 select hospitalname,pt_id,location,min(startdatetime) as 'Start',max(enddatetime) as 'End'
  from  #StartandStop
 group by hospitalname,pt_id,location

这些是我只取每个的最小开始和最大停止时得到的结果，而没有考虑患者在单位之间来回移动的情况。

   hospitalname        pt_id    location    Start                       End
   ClevelandClinic     1         A          2020-01-01 10:35:00.000     2020-01-02 12:30:00.000
   ClevelandClinic     1         B          2020-01-02 12:30:00.000     2020-01-05 07:09:00.000
   ClevelandClinic     1         C          2020-01-04 19:30:00.000     2020-01-08 20:02:00.000
   ClevelandClinic     1         D          2020-01-05 07:09:00.000     2020-01-08 00:00:00.000

这些是我想要得到的结果：

 Hospital        Patient     Location     Start                          Stop
 ClevelandClinic    1        A            2020-01-01 10:35:00.000        2020-01-02 12:30:00.000
 ClevelandClinic    1        B            2020-01-02 12:30:00.000        2020-01-04 19:30:00.000
 ClevelandClinic    1        C            2020-01-04 19:30:00.000        2020-01-05 18:44:00.000
 ClevelandClinic    1        B            2020-01-05 18:44:00.000        2020-01-05 07:09:00.000
 ClevelandClinic    1        D            2020-01-05 07:09:00.000        2020-01-08 00:00:00.000
 ClevelandClinic    1        C            2020-01-08 00:00:00.000        2020-01-08 20:02:00.000

请告知是否有办法将同一地点的第一次和第二次访问标记或区分为不同。 谢谢！

Answer 1

ALTER TABLE #StartandStop ADD color INT

DECLARE @color INT
SELECT @color = 0

UPDATE ss SET color = @color, @color = CASE WHEN s.Location <> s.LastLocation THEN @color + 1 ELSE @color END
FROM #StartandStop ss JOIN (SELECT hospitalname, pt_id, Location, LAG(location) OVER (ORDER BY hospitalname,pt_id,startdatetime,location) AS LastLocation, startdatetime, enddatetime 
    FROM #StartandStop) s ON (ss.hospitalname = s.hospitalname AND ss.pt_id = s.pt_id AND ss.location = s.location AND ss.startdatetime = s.startdatetime AND ss.enddatetime = s.enddatetime)

SELECT hospitalname AS Hospital, pt_id AS Patient, MIN(Location) AS Location, MIN(startdatetime) AS Start, MAX(enddatetime) AS Stop
FROM #StartandStop
GROUP BY hospitalname,pt_id,color
ORDER BY 1,2,4,3