Question

I have the following data being returned from a query. Essentially I am putting this in a temp table so it is now in a temp table that I can query off of(Obviously a lot more data in real life, I am just showing an example):

EmpId      Date
1        2011-01-01
1        2011-01-02
1        2011-01-03
2        2011-02-03
3        2011-03-01
4        2011-03-02
5        2011-01-02

I need to return only EmpId’s that have 30 or more consecutive days in the date column. I also need to return the day count for these employees that have 30 or more consecutive days. There could potentially be 2 or more sets of different consecutive days that are 30 or more days. iIn this instance I would like to return multiple rows. So if an employee has a date from 2011-01-01 to 2011-02-20 then return this and the count in one row. Then if this same employee has dates of 2011-05-01 to 2011-07-01 then return this in another row. Essentially all breaks in consecutive days are treated as a seperate record.

Answer 1

Using DENSE_RANK should do the trick:

;WITH sampledata
    AS (SELECT 1 AS id, DATEADD(day, -0, GETDATE())AS somedate
        UNION ALL SELECT 1, DATEADD(day, -1, GETDATE())
        UNION ALL SELECT 1, DATEADD(day, -2, GETDATE())
        UNION ALL SELECT 1, DATEADD(day, -3, GETDATE())
        UNION ALL SELECT 1, DATEADD(day, -4, GETDATE())
        UNION ALL SELECT 1, DATEADD(day, -5, GETDATE())
        UNION ALL SELECT 1, DATEADD(day, -10, GETDATE())
        UNION ALL SELECT 1, '2011-01-01 00:00:00'
        UNION ALL SELECT 1, '2010-12-31 00:00:00'
        UNION ALL SELECT 1, '2011-02-01 00:00:00'
        UNION ALL SELECT 1, DATEADD(day, -10, GETDATE())
        UNION ALL SELECT 2, DATEADD(day, 0, GETDATE())
        UNION ALL SELECT 2, DATEADD(day, -1, GETDATE())
        UNION ALL SELECT 2, DATEADD(day, -2, GETDATE())
        UNION ALL SELECT 2, DATEADD(day, -6, GETDATE())
        UNION ALL SELECT 3, DATEADD(day, 0, GETDATE())
        UNION ALL SELECT 4, DATEADD(day, 0, GETDATE())
        UNION ALL SELECT 5, DATEADD(day, 0, GETDATE()))
   , ranking
    AS (SELECT *, DENSE_RANK()OVER(PARTITION BY id ORDER BY DATEDIFF(day, 0, somedate)) - DATEDIFF(day, 0, somedate)AS dategroup
          FROM sampledata)
    SELECT id
         , MIN(somedate)AS range_start
         , MAX(somedate)AS range_end
         , DATEDIFF(day, MIN(somedate), MAX(somedate)) + 1 AS consecutive_days
      FROM ranking
     GROUP BY id, dategroup
     --HAVING DATEDIFF(day, MIN(somedate), MAX(somedate)) + 1 >= 30 --change as needed
     ORDER BY id, range_start