WHERE语句
===
使用where语句来设定select,update,delete语句数据抽出条件
## 实战
```
> select * from users;
> select * from users where score > 20 ;
> select * from users where score < 30;
> select * from users where score > 20 and score < 30;
> select * from users where team = '勇士';
> select * from users where team != '勇士';
> select * from users where player like '阿%'; # 以阿开头
> select * from users where player like '阿_'; # 两个字符
```