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Help with CTE please.

  • April 1, 2014 at 9:54 am

    #285291

    Hello,

    I am trying but failing miserably with this CTE. Thank you very much for your assistance.

    .

    DECLARE @t TABLE (rowId INT IDENTITY, GradeId INT, DateOfMfg DATETIME)

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (107, '2014-04-01 08:02:27.203')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (107, '2014-04-01 08:12:32.113')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (107, '2014-04-01 08:34:13.547')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (123, '2014-04-01 09:52:39.107')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (123, '2014-04-01 10:02:57.220')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (123, '2014-04-01 11:05:17.307')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (107, '2014-04-01 12:12:27.203')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (107, '2014-04-01 13:02:32.113')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (107, '2014-04-01 13:34:13.547')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (123, '2014-04-01 14:52:39.107')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (123, '2014-04-01 15:02:57.220')

    INSERT INTO @t (GradeId, DateOfMfg) VALUES (123, '2014-04-01 15:05:17.307')

    .

    Trying to group the GradeId column, detecting changes in the group. At each group, I need to capture the first DateOfMfg as the BeginDate, then when the GradeId changes, the DateOfMfg as the EndDate.

    GradeIdBeginDtEndDt

    1072014-04-01 08:02:27.2032014-04-01 08:34:13.547

    1232014-04-01 09:52:39.1072014-04-01 11:05:17.307

    1072014-04-01 12:12:27.2032014-04-01 13:34:13.547

    1232014-04-01 14:52:39.1072014-04-01 15:05:17.307

    .

    Here is my horrible attempt at a CTE. I thought I was close but definitely not.

    ;WITH CTE1

    as

    (

    SELECT r.GradeId, r.DateofMfg, datediff(MINUTE, '19000101', r.DateofMfg)

    - ROW_NUMBER() OVER (Partition by r.GradeId order by r.GradeId, r.DateofMfg) as GroupID

    FROM @t r

    )

    SELECT

    GradeId,

    min(DateofMfg) as startdate,

    max(DateofMfg) as enddate

    FROM CTE1

    GROUP BY GradeId, GroupID

    .

    Thank you all for your time. -John

  • April 1, 2014 at 10:12 am

    #1702122

    You were really close to the solution.

    WITH CTE1

    as

    (

    SELECT r.GradeId,

    r.DateofMfg,

    ROW_NUMBER() OVER (order by r.DateofMfg)

    - ROW_NUMBER() OVER (Partition by r.GradeId order by r.DateofMfg) as GroupID

    FROM @t r

    )

    SELECT

    GradeId,

    min(DateofMfg) as startdate,

    max(DateofMfg) as enddate

    FROM CTE1

    GROUP BY GradeId, GroupID

    ORDER BY startdate

    Luis C.
    General Disclaimer:
    Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?

    How to post data/code on a forum to get the best help: Option 1 / Option 2

  • April 1, 2014 at 10:48 am

    #1702144

    Thank you very much. That worked perfectly.

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