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CREATE TABLE Articles ( article_id serial PRIMARY KEY ); CREATE TABLE Keywords ( kid serial PRIMARY KEY, article_id INT NOT NULL, keyword VARCHAR (50) ); INSERT INTO Keywords (article_id, keyword) VALUES (0, 'a'), (0, 'b'), (0, 'c'), (1, 'a'), (1, 'd'), (2, 'a'), (2, 'b'), (2, 'c'); INSERT INTO Articles (article_id) VALUES (0), (1), (2); WITH A AS (SELECT A.article_id AS id1, A.article_id AS id2 FROM Articles A) SELECT A.id1, A.id2 FROM A a CROSS JOIN A b