Listing 2: T-SQL Query that Calculates Grouping Factor
SELECT storeid, dt,
  (SELECT MIN(dt)
   FROM dbo.Sales AS S2
   WHERE S2.storeid = S1.storeid
     AND S2.dt >= S1.dt
     AND NOT EXISTS
       (SELECT *
        FROM dbo.Sales AS S3
        WHERE S3.storeid = S2.storeid
          AND S3.dt - 1 = S2.dt)) AS grp
FROM dbo.Sales AS S1
WHERE dt BETWEEN '20050101' AND '20050131';