MySQL几种更新操作的案例分析

CREATE TABLE `hw_account` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) DEFAULT NULL,
  `balance` int(11) DEFAULT NULL,
  `status` varchar(20) DEFAULT NULL,
  `create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4;

# 数据查询
select * from hw_account where id = 1;

# 数据更新
update hw_account set balance = 5 where id = 1;

# 数据查询
select * from hw_account where id = 1;

# 数据更新
update hw_account set balance = 5 , version = version + 1 
  where id = 1 and version = n;
  
# 判断是否成功  
if row < 1 {
   回滚
}

# 数据更新
update hw_account set balance = balance + @change_num , version = version + 1 
  where id = 1 and version = n;
  
# 判断是否成功  
if row < 1 {
   回滚
}   

# 伪代码

if (获取分布式锁) {
  update hw_account set balance = @balance where id = 1;
} else {
  # 进入等待，或者进行自旋获取锁
}

update hw_account set `status` = 1 where id = 1;