![]() Note that the sequence generator may have conflicts with IDs that were already inserted using explicit values. Continue using ID generator INSERT INTO teams (name ) VALUES ( 'Liverpool' ) - ID 7 is assigned Insert ID 8 explicitly INSERT INTO teams VALUES ( 8, 'Everton' ) If you insert an ID value explicitly, it has no effect on the sequence generator, and its next value remains unchanged and will be used when you insert subsequent rows: SERIAL - Specify Initial Value and Increment ERROR: null value in column "id" violates not-null constraint INSERT INTO teams VALUES ( 0, 'Reserved' ) ![]() INSERT INTO teams VALUES ( NULL, 'Some team' ) In MySQL these 2 values force ID generation, but this is not applied to PostgerSQL: Note that you cannot insert NULL, but can insert 0. Specify DEFAULT INSERT INTO teams VALUES ( DEFAULT, 'Manchester City' ) ![]() Omit serial column INSERT INTO teams (name ) VALUES ( 'Aston Villa' ) To generate a ID value, you can omit the SERIAL column in INSERT statement, or specify DEFAULT keyword: If you need a SERIAL column to be unique, you have to specify UNIQUE or PRIMARY KEY explicitly. Id INT NOT NULL DEFAULT NEXTVAL ( 'teams_id_seq' ) , ![]() is equivalent to CREATE SEQUENCE teams_id_seq When you define a SERIAL column, PostgreSQL automatically changes column to NOT NULL, creates a sequence tablename_serialcol_seq and DEFAULT NEXTVAL to select ID values from the sequence only if they are not supplied in INSERT statement: ![]()
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