2 Replies Latest reply: Apr 2, 2011 5:05 AM by 811822 RSS

    MINUS Set Operator

    811822
      Hi,

      I was browsing through the examples of the manual and found this particular one peculiar:
      Example 19–16 Set Operators: MINUS Query
      <query id="q1BBAQuery"><![CDATA[
      R1 MINUS R2
      ]]></query>
      Example 19–17 Set Operators: MINUS Relation Input R1
      Timestamp Tuple Kind Tuple
      1500: + 10,40
      2000: + 10,30
      2000: - 10,40
      3000: - 10,30
      Example 19–18 Set Operators: MINUS Relation Input R2
      Timestamp Tuple Kind Tuple
      1000: + 11,20
      2000: + 10,40
      3000: - 10,30
      Example 19–19 Set Operators: MINUS Relation Output
      Timestamp Tuple Kind Tuple
      1000: + 10,40.0
      2000: - 10,40.0
      Why is the tuple 10,40 inserted at 1000? Is MINUS the difference when R2(t) is subtracted from R1(t)?