How do I group on continuous ranges

问题

I know some basic sql, but this one is beyond me. I have looked high and low but no dice. I need a view of the following data, I can do this in the application layer code. But unfortunately for this particular one, the code must be put in the data layer.

I am using T-SQL.

Table

Date      Crew       DayType
01-02-11  John Doe  SEA  
02-02-11  John Doe  SEA  
03-02-11  John Doe  SEA  
04-02-11  John Doe  HOME  
05-02-11  John Doe  HOME  
06-02-11  John Doe  SEA

I need a view like this

DateFrom  DateTo    Name      DayType
01-02-11  03-02-11  John Doe  SEA
04-02-11  05-02-11  John Doe  HOME
06-02-11  06-02-11  John Doe  SEA

Unfortunately the base table is required for application layer to be in the format show. Is this possible to do in query?

Thanks

Luke

回答1:

WITH    q AS
        (
        SELECT  *,
                ROW_NUMBER() OVER (PARTITION BY crew, dayType ORDER BY [date]) AS rnd,
                ROW_NUMBER() OVER (PARTITION BY crew ORDER BY [date]) AS rn
        FROM    mytable
        )
SELECT  MIN([date]), MAX([date]), crew AS name, dayType
FROM    q
GROUP BY
        crew, dayType, rnd - rn

This article may be of interest to you:

Things SQL needs: SERIES()

回答2:

WITH grouped AS (
  SELECT
    *,
    grp = DATEDIFF(day, 0, Date) -
          ROW_NUMBER() OVER (PARTITION BY Crew, DayType ORDER BY Date)
  FROM @testtable
)
SELECT
  DateFrom = MIN(Date),
  DateTo = MAX(Date),
  Name = Crew,
  DayType
FROM grouped
GROUP BY Crew, DayType, grp;

Basically, same as Quassnoi's solution, but using one ROW_NUMBER fewer yields a better execution plan.

回答3:

SELECT MIN(Date) AS DateFrom,MAX(Date) AS DateTo, Crew, DayType FROM yourTableName GROUP BY Crew, DayType

回答4:

Something Like:

SELECT Crew, DayType, MIN(Date) AS SomeDate1, MAX(Date) AS SomeDate2 
FROM Mytable 
GROUP BY Crew, DayType

回答5:

Select Min(Date) DateFrom, Max(Date) DateTo, Crew Name,DayType From Mytable Group By Crew,DayType

try this.

来源：https://stackoverflow.com/questions/5662545/how-do-i-group-on-continuous-ranges

标签

sql

sql-server

sql-server-2005

tsql

gaps-and-islands