Is it possible to have unique together constraint on a SET of columns in PostgreSQL?












0















What I want to achieve is the following:



CREATE TABLE foo (
bar1 int,
bar2 int,
type varchar(16),
FOREIGN KEY bar1 REFERENCES bar(id),
FOREIGN KEY bar2 REFERENCES bar(id)
);

ALTER TABLE foo ADD CONSTRAINT unique_link (bar1, bar2);

INSERT INTO foo (bar1, bar2, type) VALUES (1, 2, 'simple link')
--next line should fail, as {2, 1} as a set is already present, just in a different order
INSERT INTO foo (bar1, bar2, type) VALUES (2, 1, 'simple link')


Is it possible in any way? Maybe with some triggers maybe, or some auto calculated hashes of the bar* columns? Thanks for the help!









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    0















    What I want to achieve is the following:



    CREATE TABLE foo (
    bar1 int,
    bar2 int,
    type varchar(16),
    FOREIGN KEY bar1 REFERENCES bar(id),
    FOREIGN KEY bar2 REFERENCES bar(id)
    );

    ALTER TABLE foo ADD CONSTRAINT unique_link (bar1, bar2);

    INSERT INTO foo (bar1, bar2, type) VALUES (1, 2, 'simple link')
    --next line should fail, as {2, 1} as a set is already present, just in a different order
    INSERT INTO foo (bar1, bar2, type) VALUES (2, 1, 'simple link')


    Is it possible in any way? Maybe with some triggers maybe, or some auto calculated hashes of the bar* columns? Thanks for the help!









    share







    New contributor




    Hodossy Szabolcs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.























      0












      0








      0








      What I want to achieve is the following:



      CREATE TABLE foo (
      bar1 int,
      bar2 int,
      type varchar(16),
      FOREIGN KEY bar1 REFERENCES bar(id),
      FOREIGN KEY bar2 REFERENCES bar(id)
      );

      ALTER TABLE foo ADD CONSTRAINT unique_link (bar1, bar2);

      INSERT INTO foo (bar1, bar2, type) VALUES (1, 2, 'simple link')
      --next line should fail, as {2, 1} as a set is already present, just in a different order
      INSERT INTO foo (bar1, bar2, type) VALUES (2, 1, 'simple link')


      Is it possible in any way? Maybe with some triggers maybe, or some auto calculated hashes of the bar* columns? Thanks for the help!









      share







      New contributor




      Hodossy Szabolcs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.












      What I want to achieve is the following:



      CREATE TABLE foo (
      bar1 int,
      bar2 int,
      type varchar(16),
      FOREIGN KEY bar1 REFERENCES bar(id),
      FOREIGN KEY bar2 REFERENCES bar(id)
      );

      ALTER TABLE foo ADD CONSTRAINT unique_link (bar1, bar2);

      INSERT INTO foo (bar1, bar2, type) VALUES (1, 2, 'simple link')
      --next line should fail, as {2, 1} as a set is already present, just in a different order
      INSERT INTO foo (bar1, bar2, type) VALUES (2, 1, 'simple link')


      Is it possible in any way? Maybe with some triggers maybe, or some auto calculated hashes of the bar* columns? Thanks for the help!







      postgresql postgresql-11





      share







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      Hodossy Szabolcs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.










      share







      New contributor




      Hodossy Szabolcs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.








      share



      share






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      asked 6 mins ago









      Hodossy SzabolcsHodossy Szabolcs

      1011




      1011




      New contributor




      Hodossy Szabolcs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.





      New contributor





      Hodossy Szabolcs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      Hodossy Szabolcs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






















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