Mybatis-plus QueryWrapper使用

   QueryWrapper<UserEntity> userWrapper = new QueryWrapper<>();
        userWrapper.and(wrapper->wrapper.eq("username", "test2").or().eq("username", "test2"))
                .or(wrapper -> wrapper.like("username", "test2").or().like("username", "test2"));

# SELECT id,username,pwd,date_u,time_u,u_num,img FROM student WHERE ( username = ? OR username = ? ) OR ( username LIKE ? OR username LIKE ? )

  QueryWrapper<UserEntity> userWrapper = new QueryWrapper<>();
        userWrapper.and(wrapper->wrapper.eq("username", "test2").or().eq("username", "test2"))
                .and(wrapper -> wrapper.like("username", "test2").or().like("username", "test2"));
#SELECT id,username,pwd,date_u,time_u,u_num,img FROM student WHERE ( username = ? OR username = ? ) AND ( username LIKE ? OR username LIKE ? )

 QueryWrapper userWrapper = new QueryWrapper<>();
        userWrapper.apply("select stamp_u,username,name,age from student,rel_student where student.id=rel_student.id");

#select stamp_u,username,name,age from student,rel_student where student.id=rel_student.id 

     QueryWrapper<UserEntity> userWrapper = new QueryWrapper<>();
        userWrapper.eq("username", "test").eq("username", "test");

#select * from student WHERE username = ?  and  username = ?