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CREATE TABLE users ( id SERIAL PRIMARY KEY, name TEXT ); CREATE TABLE notes ( id SERIAL PRIMARY KEY, user_id INT, content TEXT, CONSTRAINT fk_user FOREIGN KEY(user_id) REFERENCES users(id) );
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INSERT INTO users(name) VALUES ('Alice'), ('Bob'); INSERT INTO notes(user_id, content) VALUES (1, 'Alice Note 1'), (1, 'Alice Note 2'), (2, 'Bob Note');
2 rows affected
3 rows affected
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SELECT notes.*, users.name FROM notes INNER JOIN users ON notes.user_id = users.id
id user_id content name
1 1 Alice Note 1 Alice
2 1 Alice Note 2 Alice
3 2 Bob Note Bob
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BEGIN; UPDATE users SET id=3 WHERE id=1; UPDATE notes SET user_id=3 WHERE user_id=1; COMMIT;
ERROR: update or delete on table "users" violates foreign key constraint "fk_user" on table "notes" DETAIL: Key (id)=(1) is still referenced from table "notes".
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