谷粒学院项目实战20——mp实现复杂条件查询

我们一般使用QueryWrapper来实现在mp中的复杂条件查询。

    //复杂查询操作
    @Test
    public void testSelectQuery() {
        // user whose age>=30
        QueryWrapper wrapper = new QueryWrapper<User>();
        wrapper.ge("age", 30);
        List<User> users = userMapper.selectList(wrapper);
        for(User user : users) {
            System.out.println(user);
        }

        // user whose name.equals("风清扬")
        QueryWrapper wrapper2 = new QueryWrapper<User>();
        wrappe2r.eq("name","风清扬");
        List<User> users2 = userMapper.selectList(wrapper2);
        for(User user : users2) {
            System.out.println(user);
        }

        System.out.println("-----------");
        QueryWrapper wrapper3 = new QueryWrapper<User>();
        // user whose name have character “岳”
        wrapper3.like("name","岳");
        List<User> users3 = userMapper.selectList(wrapper3);
        for(User user : users3) {
            System.out.println(user);
        }


        System.out.println("-----------");
        QueryWrapper wrapper4 = new QueryWrapper<User>();
        // users order by id asc
        wrapper4.orderByAsc("id");
        List<User> users4 = userMapper.selectList(wrapper4);
        for(User user : users4) {
            System.out.println(user);
        }

        System.out.println("-----------");
        QueryWrapper wrapper5 = new QueryWrapper<User>();
        // splicing sql
        wrapper5.last("limit 2");
        List<User> users5 = userMapper.selectList(wrapper5);
        for(User user : users5) {
            System.out.println(user);
        }


        System.out.println("-----------");
        QueryWrapper wrapper6 = new QueryWrapper<User>();
        // assign the content selected
        wrapper6.select("id", "name");
        List<User> users6 = userMapper.selectList(wrapper6);
        for(User user : users6) {
            System.out.println(user);
        }
    }