7、分页

7、分页

思考：为什么要分页？

• 减少数据的处理量

7、1使用Limit分页

语法：SELECT * from user limit startIndex,pageSize;
SELECT * from user limit 3; #[0,n]

使用Mybatis实现啊分页，核心SQL

​ 1.接口

    //分页
    List<User> getUserByLimit(HashMap<String, Integer> map);

​ 2.Mapper.xml

    <select id="getUserByLimit" parameterType="map" resultType="user" resultMap="UserMap">
        select * from mybatis.user limit #{starIndex},#{pageSize}
    </select>

​ 3.测试

    @Test
    public void getUserByLimit(){
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        HashMap<String, Integer> map = new HashMap<>();
        map.put("starIndex",0);
        map.put("pageSize",2);
        List<User> userByLimit = mapper.getUserByLimit(map);
        for (User user : userByLimit) {
            System.out.println(user);
        }


        sqlSession.close();
    }