ALTER TABLE `t_app_user`
    ADD COLUMN `balance` decimal(10, 2) NOT NULL DEFAULT 0.00 COMMENT '余额' AFTER `points`;

ALTER TABLE `t_exchange_code_use_record`
    MODIFY COLUMN `order_id` bigint NULL DEFAULT 0 COMMENT '订单ID，0表示兑换入账';

CREATE INDEX `idx_exchange_code_use_record_user_time`
    ON `t_exchange_code_use_record` (`user_id`, `create_time`);