SELECT COUNT(*) INTO @col_exists FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'withdrawals' AND COLUMN_NAME = 'method';

SET @ddl = IF(@col_exists = 0,
  'ALTER TABLE `withdrawals` ADD COLUMN `method` TINYINT(1) NOT NULL DEFAULT 0 AFTER `content`, ADD COLUMN `account` VARCHAR(255) NOT NULL DEFAULT '''' AFTER `method`, ADD COLUMN `qr_code_url` VARCHAR(500) NOT NULL DEFAULT '''' AFTER `account`',
  'SELECT 1');

PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;