CREATE TABLE payments (
    payer_id INTEGER NOT NULL,
    recipient_id INTEGER NOT NULL,
    amount INTEGER NOT NULL
);

INSERT INTO payments (payer_id, recipient_id, amount) VALUES
(1, 2, 100),
(2, 1, 150),
(1, 3, 200),
(3, 1, 250),
(2, 4, 300),
(4, 2, 350),
(3, 5, 400),
(5, 3, 450),
(6, 7, 500); -- No two-way transaction