CREATE TABLE split_payments (
  id SERIAL PRIMARY KEY,
  from_participant_id INTEGER NOT NULL REFERENCES participants(id),
  to_participant_id   INTEGER NOT NULL REFERENCES participants(id),
  amount              DECIMAL(10,2) NOT NULL CHECK (amount > 0),
  payment_date        DATE NOT NULL,
  notes               TEXT,
  linked_transaction_id INTEGER REFERENCES transactions(id) ON DELETE SET NULL,
  created_at          TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE INDEX idx_split_payments_from ON split_payments(from_participant_id);
CREATE INDEX idx_split_payments_to   ON split_payments(to_participant_id);