SUM returning different values when WHERE clause is changed

• mediacommentry

  SSC-Addicted

  Points: 408

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  January 29, 2019 at 1:19 am

  #376878

  Hi,

  I have a strange issue. I have a table UserActivity with 2 columns, UserId and PointsAllocated. User = 2456, with 11 455 records. PointsAllocated is 0 for some records and values ( 7, 51, 200 etc) for other records.
  I have a simple query,  SELECT UserId, SUM(PointsAllocated) FROM UserActivity WHERE UserId = 2456 GROUP BY UserId and I'm getting 162 547.
  But where I write  SELECT UserId, SUM(PointsAllocated) FROM UserActivity WHERE UserId = 2456 AND PointsAllocated > 0 GROUP BY UserId I'm getting a different value, higher value, 337074.

  I want to understand why is it so, because when 0 is added to a number, a number doesn't change, why is that when I exclude the values I get more value returned.

• ChrisM@Work

  SSC Guru

  Points: 186127

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  January 29, 2019 at 2:08 am

  #2020374

  mediacommentry - Tuesday, January 29, 2019 1:19 AM

  Hi,

  I have a strange issue. I have a table UserActivity with 2 columns, UserId and PointsAllocated. User = 2456, with 11 455 records. PointsAllocated is 0 for some records and values ( 7, 51, 200 etc) for other records.
  I have a simple query,  SELECT UserId, SUM(PointsAllocated) FROM UserActivity WHERE UserId = 2456 GROUP BY UserId and I'm getting 162 547.
  But where I write  SELECT UserId, SUM(PointsAllocated) FROM UserActivity WHERE UserId = 2456 AND PointsAllocated > 0 GROUP BY UserId I'm getting a different value, higher value, 337074.

  I want to understand why is it so, because when 0 is added to a number, a number doesn't change, why is that when I exclude the values I get more value returned.

  Run this:
  SELECT
   UserId,
   PositivePoints = SUM(CASE WHEN PointsAllocated > 0 THEN PointsAllocated ELSE 0 END),
   NegativePoints = SUM(CASE WHEN PointsAllocated < 0 THEN PointsAllocated ELSE 0 END)
  FROM UserActivity
  WHERE UserId = 2456
  GROUP BY UserId

  ^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

  For fast, accurate and documented assistance in answering your questions, please read this article.
  Understanding and using APPLY, (I) and (II) Paul White
  Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

• Martin Schoombee

  SSCoach

  Points: 19134

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  January 29, 2019 at 6:13 am

  #2020393

  You more than likely have negative numbers in that field.