一、数据库表结构以及数据

CREATE TABLE `forlan_score` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
  `student_name` varchar(255) DEFAULT NULL COMMENT '学生名称',
  `score` int(20) DEFAULT '-1' COMMENT '分数',
	`course_name` varchar(255) DEFAULT NULL COMMENT '课程',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 ROW_FORMAT=DYNAMIC COMMENT='学生成绩表';
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (1, '小明', 70, '数学');
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (2, '小红', 65, '英语');
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (3, '小林', 100, '数学');
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (4, '小黄', 100, '语文');
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (5, '小东', 80, '语文');
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (6, '小美', 90, '英语');
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (7, '小伟', 88, '英语');
INSERT INTO `test`.`forlan_score` (`id`, `student_name`, `score`, `course_name`) VALUES (8, '小小', 100, '数学');

二、实现排名（不分组）

1、不重复，连续

1.1、不同版本实现

1）mysql5.7实现

• 使用自定义变量（外部sql）

SET @cur_rank := 0;
SELECT
	student_name,
	score,
	@cur_rank := @cur_rank + 1 AS ranking 
FROM
	forlan_score 
ORDER BY
	score DESC;

• 使用自定义变量（内部sql）（推荐）

SELECT
	fs.student_name,
	fs.score,
	( @cur_rank := @cur_rank + 1 ) AS ranking 
FROM
	forlan_score fs,
	( SELECT @cur_rank := 0 ) r 
ORDER BY
	score DESC;

2）mysql8实现

ROW_NUMBER()

SELECT
	student_name,
	score,
	ROW_NUMBER() OVER ( ORDER BY score DESC ) AS ranking 
FROM
	forlan_score;

1.2、效果

+--------------+-------+---------+
| student_name | score | ranking |
+--------------+-------+---------+
| 小林         |   100 |       1 |
| 小黄         |   100 |       2 |
| 小小         |   100 |       3 |
| 小美         |    90 |       4 |
| 小伟         |    88 |       5 |
| 小东         |    80 |       6 |
| 小明         |    70 |       7 |
| 小红         |    65 |       8 |
+--------------+-------+---------+

2、并列排名，连续

2.1、不同版本实现

1）mysql5.7实现

• 使用自定义变量 + IF

SELECT
	fs.student_name,
	fs.score,
	IF( @pre_score = fs.score, @cur_rank, @cur_rank := @cur_rank + 1 ) AS ranking,
	@pre_score := fs.score 
FROM
	forlan_score fs,( SELECT @cur_rank := 0, @pre_score := NULL ) r 
ORDER BY
	fs.score DESC;

• 使用自定义变量 + CASE WHEN

SELECT
	fs.student_name,
	fs.score,
	(
		CASE
			WHEN @pre_score = fs.score THEN @cur_rank 
			WHEN @pre_score := fs.score THEN @cur_rank := @cur_rank + 1 
		END 
	) AS ranking 
	FROM
		forlan_score fs,(SELECT @cur_rank := 0,@pre_score := NULL) r 
ORDER BY
	fs.score DESC;

2）mysql8实现

DENSE_RANK()

SELECT
	student_name,
	score,
	DENSE_RANK() OVER ( ORDER BY score DESC ) AS ranking 
FROM
	forlan_score;

2.2、效果

+--------------+-------+---------+
| student_name | score | ranking |
+--------------+-------+---------+
| 小林         |   100 |       1 |
| 小黄         |   100 |       1 |
| 小小         |   100 |       1 |
| 小美         |    90 |       2 |
| 小伟         |    88 |       3 |
| 小东         |    80 |       4 |
| 小明         |    70 |       5 |
| 小红         |    65 |       6 |
+--------------+-------+---------+

3、并列排名，不连续

3.1、不同版本实现

1）mysql5.7实现

• 使用自定义变量 + IF

SELECT
	fs.student_name,
	fs.score,
	@row_num := @row_num + 1,
	IF( @pre_score = fs.score, @cur_rank, @cur_rank := @row_num ) AS ranking,
	@pre_score := fs.score 
FROM
	forlan_score fs,
	(SELECT @cur_rank := 0,@pre_score := NULL,@row_num := 0 ) r 
ORDER BY
	fs.score DESC;

• 使用自定义变量 + CASE WHEN

SELECT
	fs.student_name,
	fs.score,
	@row_num := @row_num + 1,
	( CASE WHEN @pre_score = fs.score THEN @cur_rank WHEN @pre_score := fs.score THEN @cur_rank := @row_num END ) AS ranking 
FROM
	forlan_score fs,
	( SELECT @cur_rank := 0, @pre_score := NULL, @row_num := 0 ) r 
ORDER BY
	fs.score DESC;

2）mysql8实现

RANK()

SELECT
	student_name,
	score,
	RANK() OVER ( ORDER BY score DESC ) AS ranking 
FROM
	forlan_score;

3.2、效果

+--------------+-------+---------+
| student_name | score | ranking |
+--------------+-------+---------+
| 小林         |   100 |       1 |
| 小黄         |   100 |       1 |
| 小小         |   100 |       1 |
| 小美         |    90 |       4 |
| 小伟         |    88 |       5 |
| 小东         |    80 |       6 |
| 小明         |    70 |       7 |
| 小红         |    65 |       8 |
+--------------+-------+---------+

三、按照课程分组实现排名

1、不重复，连续

1.1、不同版本实现

1）mysql5.7实现

• 使用自定义变量 + IF

SELECT
	fs.student_name,
	fs.course_name,
	fs.score,
	IF(@cur_couse = course_name, @cur_rank := @cur_rank+1, @cur_rank :=1) AS ranking,
	@cur_couse := fs.course_name
FROM
	forlan_score fs,
	( SELECT @cur_rank := 0,  @cur_couse := NULL ) r 
ORDER BY
	fs.course_name,fs.score DESC;

2）mysql8实现

ROW_NUMBER()

SELECT
	student_name,
	course_name,
	score,
	ROW_NUMBER() OVER (PARTITION BY course_name ORDER BY course_name,score DESC) AS ranking
FROM
	forlan_score;

1.2、效果

+--------------+-------------+-------+---------+
| student_name | course_name | score | ranking |
+--------------+-------------+-------+---------+
| 小林         | 数学        |   100 |       1 |
| 小小         | 数学        |   100 |       2 |
| 小明         | 数学        |    70 |       3 |
| 小美         | 英语        |    90 |       1 |
| 小伟         | 英语        |    88 |       2 |
| 小红         | 英语        |    65 |       3 |
| 小黄         | 语文        |   100 |       1 |
| 小东         | 语文        |    80 |       2 |
+--------------+-------------+-------+---------+

2、并列排名，连续

2.1、不同版本实现

1）mysql5.7实现

• 使用自定义变量 + IF

SELECT
	fs.student_name,
	fs.course_name,
	fs.score,
	IF(@cur_couse = course_name, IF( @pre_score = fs.score, @cur_rank, @cur_rank := @cur_rank+1 ), @cur_rank :=1) AS ranking,
	@pre_score := fs.score,
	@cur_couse := fs.course_name
FROM
	forlan_score fs,
	( SELECT @cur_rank := 0, @pre_score := NULL, @cur_couse := NULL ) r 
ORDER BY
	fs.course_name,fs.score DESC;