breek rij_nummer () reeks op basis van vlagvariabele

Uitgaande van SQL Server is hier een voorbeeld:

DECLARE @T table (id int, [month] char(3), flag bit)

INSERT INTO @T
VALUES
(111, 'jan', 1)
,(111, 'feb', 1)
,(111, 'mar', 1)
,(111, 'apr', 0)
,(111, 'may', 0)
,(111, 'jun', 1)
,(222, 'jan', 1)
,(222, 'feb', 1)
,(222, 'mar', 0)
,(222, 'apr', 0)
,(222, 'may', 0)
,(222, 'jun', 1)

SELECT
    id
    , [month]
    , flag
    , ROW_NUMBER() OVER (PARTITION BY id, section ORDER BY monthNum) [order]
FROM
    (
        SELECT
            id
            , [month]
            , monthNum
            , flag
            , SUM(CASE WHEN newValue = 1 THEN 1 ELSE 0 END) OVER (PARTITION BY id ORDER BY monthNum) section
        FROM
            (
                SELECT
                    id
                    , [month]
                    , monthNum
                    , flag
                    , CASE WHEN LAG(flag, 1, ABS(flag - 1)) OVER (PARTITION BY id ORDER BY monthNum) = flag THEN 0 ELSE 1 END newValue
                FROM
                    (
                        SELECT
                            id
                            , [month]
                            , MONTH(CAST('1 ' + [month] + ' 17' AS datetime)) monthNum
                            , flag
                        FROM @T
                    ) Q
            ) Q2
    ) Q3