//多条件查询  and条件  和  or条件
@Test
public  void test_01(){QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.like("name","a").between("age",20,30).or().isNotNull("email");List<User> users = userMapper.selectList(queryWrapper);
}//排序   降序和升序
@Test
public  void test2(){QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.orderByDesc("age").orderByAsc("id");List<User> users = userMapper.selectList(queryWrapper);
}//查询指定列  指定查询name列和age列
public  void  test5(){QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.select("name","age");List<User> users = userMapper.selectList(queryWrapper);
}//带条件判断
@Test
public  void test6(){String name="xx";Integer age = 19;QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.eq(StringUtils.isNotBlank(name),"name",name);queryWrapper.eq(age!=null && age>18,"age",age);List<User> users = userMapper.selectList(queryWrapper);
}