为了得到最大的性能，一般数据库都有并发机制，不过带来的问题就是数据访问的冲突。为了解决这个问题，大多数数据库用的方法就是数据的锁定.-In order to get the maximum performance, a general mechanism for the database have complicated, but the problem is caused by data access conflicts. To solve this problem, the majority of the database is used to lock data.