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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')

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')

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')

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')

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