Details

    • Type: Sub-task
    • Status: Closed
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 4.2.0, 3.2.0
    • Labels:
    • old issue number:
      36

      Description

      A semi-join between two tables returns rows from the first table where one or more matches are found in the second table. The difference between a semi-join and a conventional join is that rows in the first table will be returned at most once. Even if the second table contains two matches for a row in the first table, only one copy of the row will be returned. Semi-joins are written using the EXISTS or IN constructs.

      An anti-join is the opposite of a semi-join and is written using the NOT EXISTS or NOT IN constructs.

      There's a pretty good write-up [here] (http://www.dbspecialists.com/files/presentations/semijoins.html) on semi/anti joins.

        Attachments

        1. 167.patch
          188 kB
          Maryann Xue
        2. 167-2.patch
          189 kB
          Maryann Xue

          Activity

            People

            • Assignee:
              maryannxue Maryann Xue
              Reporter:
              jamestaylor James Taylor
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              • Created:
                Updated:
                Resolved: