CREATE TABLE IF NOT EXISTS order_items (
     id         BIGSERIAL    PRIMARY KEY,
     order_id   BIGINT       NOT NULL REFERENCES orders(id),
     product_id BIGINT       NOT NULL REFERENCES products(id),
     quantity   INTEGER      NOT NULL,
     unit_price NUMERIC(10,2) NOT NULL
 );
 
 CREATE INDEX idx_order_items_order_id ON order_items(order_id);
 CREATE INDEX idx_order_items_product_id ON order_items(product_id);