//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);
}