[求助]一张表查询各班级总分前三名

新手一枚,使用mysql 5.7.21.

最近在找练习题做,遇到一难题,束手无策了已经,现跪求各路大神指点一二.以下是表格结构及记录.

create table st(id int(4) primary key not null,
                        name varchar(20) not null,
        class varchar(10),
age int(10),
literture int(30),
mathemtics int(30)

);

insert into st values
(208,'泰瑞宝','07-25',19,98,59),
(209,'旺德福','07-25',28,48,114),
(210,'我太富','07-25',31,93,123),
(211,'黑宾','07-25',22,101,79),
(212,'苟无敬','07-25',24,118,90),
(213,'刘奶','07-25',23,67,79),
(218,'李问','07-23',19,108,77),
(219,'王说','07-20',28,78,99),
(220,'侯启娥','07-23',31,63,101),
(221,'沙俊德','07-21',22,120,79),
(222,'百得说','07-20',24,131,90),
(223,'尚且负','07-20',23,107,63),
(200,'沙牌雕','07-23',19,108,77),
(239,'操正德','07-20',28,78,92),
(224,'公孙蛋','07-23',33,140,83),
(226,'李凯华','07-21',22,80,79),
(229,'马闭屏','07-20',24,131,78),
(203,'陈德丽','07-21',23,97,63),
(308,'张泗世','07-23',19,108,77),
(419,'李石武','07-21',28,78,91),
(320,'王埘陸','07-23',31,63,101),
(321,'王实巴','07-21',22,110,79),
(322,'马石臼','07-25',24,111,90),
(329,'陈二式','07-23',23,107,63),
(328,'赵念一','07-23',19,98,77),
(319,'李拈迩','07-20',28,78,99),
(420,'周尓散','07-23',31,63,101),
(121,'钱式溢','07-21',22,120,59),
(422,'郑石耳','07-23',24,81,90),

(323,'吴识参','07-20',23,104,73);

要求:查询各班级总分前三名,总分相同者须保持并列.