1、首先创建对象
QueryWrapper<泛型> wrapper=new QueryWrapper();
2、常用方法
（1）like
实例：wrapper.like(“name”,”月”); –> where name like “%月%”
（2）lt
实例：wrapper.lt(“age”,20); –> where age<20
（3）between
实例：wrapper.between(“age”,10,20); –> where age between 10 and 20
（4）isNotNull
实例：wrapper.isNotNull(“name”); –>where name is not null
（5）likeRight
实例：wrapper.likeRight(“name”,”袁”); –>where name like “袁%”
（6）ge
实例：wrapper.ge(“age”,18); –>where age>=18
（7）or
实例：wrapper.likeRight(“name”,”袁”).or().lt(“age”,18); –>where name like “袁%” or age<18
（8）orderByDesc和orderByAsc
实例：wrapper.orderByDesc(“id”) –> order by id desc
wrapper.orderByAsc(“id”) –>order by id 或者order by id asc
（9）inSql
实例：wrapper.inSql(“id”,”select * from student”); –>where ….., id in(select * from student)