mysql中如何实现 row_number分组求topN的功能

业务场景：
从成绩表中，查询每门课程的top2的学生的所有信息

建表语句：

CREATE TABLE `subject` (
  `Id` int(11) NOT NULL DEFAULT '0',
  `subject_name` varchar(200) DEFAULT NULL,
  `sname` varchar(255) DEFAULT NULL,
  `score` int(11) DEFAULT NULL,
  PRIMARY KEY (`Id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

插入记录：

INSERT INTO subject VALUES(1,'语文','张三',85);
INSERT INTO subject VALUES(2,'语文','李四',72);
INSERT INTO subject VALUES(3,'语文','王五',96);
INSERT INTO subject VALUES(4,'语文','赵六',78);
INSERT INTO subject VALUES(5,'语文','刘七',81);
INSERT INTO subject VALUES(6,'数学','张三',82);
INSERT INTO subject VALUES(7,'数学','李四',99);
INSERT INTO subject VALUES(8,'数学','王五',70);
INSERT INTO subject VALUES(9,'数学','赵六',91);
INSERT INTO subject VALUES(10,'数学','刘七',78);
INSERT INTO subject VALUES(11,'英语','张三',62);
INSERT INTO subject VALUES(12,'英语','李四',93);
INSERT INTO subject VALUES(13,'英语','王五',98);
INSERT INTO subject VALUES(14,'英语','赵六',70);
INSERT INTO subject VALUES(15,'英语','刘七',52);

查询前两名sql：
mysql不支持row_number

SELECT a.*
FROM subject a
WHERE (
	SELECT COUNT(1)
	FROM subject b
	WHERE a.`subject_name` = b.`subject_name`
		AND b.`score` > a.score
) <2
ORDER BY subject_name, score DESC;

本文地址：https://blog.csdn.net/weixin_42123844/article/details/107640844