当执行MySQL新建表格table时：
例如：

create table students(
uid           int not null  auto_increment,
uname     varchar(30) not null,
uage        int not null,
primary  key (uid)
);

出现[Err] 1050 - Table ‘students’ already exists异常时,

经常报错：Table ‘users’ already exists

报错原因：创建表格重复

解决方法：添加 if not exists

create table if not exists students(
uid           int not null  auto_increment,
uname     varchar(30) not null,
uage        int not null,
primary  key (uid)
);