现有试卷信息表examination_info（exam_id试卷ID, tag试卷类别, difficulty试卷难度, duration考试时长, release_time发布时间）： id exam_id tag difficulty duration release_time 1 9001 SQL hard 60 2021-09-01 06:00:00 2 9002 SQL hard 60 2021-09-01 06:00:00 3 9003 算法 medium 80 2021-09-01 10:00:00 试卷作答记录表exam_record（uid用户ID, exam_id试卷ID, start_time开始作答时间, submit_time交卷时间, score得分）： id uid exam_id start_time submit_time score 1 1001 9001 2021-09-01 09:01:01 2021-09-01 09:31:00 78 2 1002 9001 2021-09-01 09:01:01 2021-09-01 09:31:00 81 3 1002 9002 2021-09-01 12:01:01 2021-09-01 12:31:01 81 4 1003 9001 2021-09-01 19:01:01 2021-09-01 19:40:01 86 5 1003 9002 2021-09-01 12:01:01 2021-09-01 12:31:51 89 6 1004 9001 2021-09-01 19:01:01 2021-09-01 19:30:01 85 7 1005 9003 2021-09-01 12:01:01 2021-09-01 12:31:02 85 8 1006 9003 2021-09-07 10:01:01 2021-09-07 10:21:01 84 9 1003 9003 2021-09-08 12:01:01 2021-09-08 12:11:01 40 10 1003 9002 2021-09-01 14:01:01 (NULL) (NULL) 找到每类试卷得分的前3名，如果两人最大分数相同，选择最小分数大者，如果还相同，选择uid大者。由示例数据结果输出如下： tid uid ranking SQL 1003 1 SQL 1004 2 SQL 1002 3 算法 1005 1 算法 1006 2 算法 1003 3 解释：有作答得分记录的试卷tag有SQL和算法，SQL试卷用户1001、1002、1003、1004有作答得分，最高得分分别为81、81、89、85，最低得分分别为78、81、86、40，因此先按最高得分排名再按最低得分排名取前三为1003、1004、1002。
示例1

输入

drop table if exists examination_info,exam_record;
CREATE TABLE examination_info (
    id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',
    exam_id int UNIQUE NOT NULL COMMENT '试卷ID',
    tag varchar(32) COMMENT '类别标签',
    difficulty varchar(8) COMMENT '难度',
    duration int NOT NULL COMMENT '时长',
    release_time datetime COMMENT '发布时间'
)CHARACTER SET utf8 COLLATE utf8_general_ci;

CREATE TABLE exam_record (
    id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID',
    uid int NOT NULL COMMENT '用户ID',
    exam_id int NOT NULL COMMENT '试卷ID',
    start_time datetime NOT NULL COMMENT '开始时间',
    submit_time datetime COMMENT '提交时间',
    score tinyint COMMENT '得分'
)CHARACTER SET utf8 COLLATE utf8_general_ci;

INSERT INTO examination_info(exam_id,tag,difficulty,duration,release_time) VALUES
  (9001, 'SQL', 'hard', 60, '2021-09-01 06:00:00'),
  (9002, 'SQL', 'hard', 60, '2021-09-01 06:00:00'),
  (9003, '算法', 'medium', 80, '2021-09-01 10:00:00');

INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES
(1001, 9001, '2021-09-01 09:01:01', '2021-09-01 09:31:00', 78),
(1001, 9001, '2021-09-01 09:01:01', '2021-09-01 09:31:00', 81),
(1002, 9002, '2021-09-01 12:01:01', '2021-09-01 12:31:01', 81),
(1003, 9001, '2021-09-01 19:01:01', '2021-09-01 19:40:01', 86),
(1003, 9002, '2021-09-01 12:01:01', '2021-09-01 12:31:51', 89),
(1004, 9001, '2021-09-01 19:01:01', '2021-09-01 19:30:01', 85),
(1005, 9003, '2021-09-01 12:01:01', '2021-09-01 12:31:02', 85),
(1006, 9003, '2021-09-07 10:01:01', '2021-09-07 10:21:01', 84),
(1003, 9003, '2021-09-08 12:01:01', '2021-09-08 12:11:01', 40),
(1003, 9002, '2021-09-01 14:01:01', null, null);

输出

SQL|1003|1
SQL|1004|2
SQL|1002|3
算法|1005|1
算法|1006|2
算法|1003|3
加载中...