CREATE TABLE IF NOT EXISTS orders (
  id INT AUTO_INCREMENT PRIMARY KEY,
  order_ref VARCHAR(64) NOT NULL UNIQUE,
  mobile VARCHAR(20) NULL,
  amount DECIMAL(18,2) NOT NULL,
  status ENUM('pending','paid','failed') NOT NULL DEFAULT 'pending',
  invoice_id VARCHAR(32) NULL,
  txid VARCHAR(120) NULL,
  created_at DATETIME NOT NULL,
  updated_at DATETIME NULL
) ENGINE=InnoDB;