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 算法 hard 60 2021-01-01 10:00:00 2 9002 C++ hard 80 2021-01-01 10:00:00 3 9003 C++ hard 80 2021-01-01 10:00:00 4 9004 sql medium 70 2021-01-01 10:00:00 5 9005 C++ hard 80 2021-01-01 10:00:00 6 9006 C++ hard 80 2021-01-01 10:00:00 7 9007 C++ hard 80 2021-01-01 10:00:00 8 9008 SQL medium 70 2021-01-01 10:00:00 9 9009 SQL medium 70 2021-01-01 10:00:00 10 9010 SQL medium 70 2021-01-01 10:00:00 试卷作答信息表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 2020-01-01 09:01:01 2020-01-01 09:21:59 80 2 1002 9003 2020-01-20 10:01:01 2020-01-20 10:10:01 81 3 1002 9002 2020-02-01 12:11:01 2020-02-01 12:31:01 83 4 1003 9002 2020-03-01 19:01:01 2020-03-01 19:30:01 75 5 1004 9002 2020-03-01 12:01:01 2020-03-01 12:11:01 60 6 1005 9002 2020-03-01 12:01:01 2020-03-01 12:41:01 90 7 1006 9001 2020-05-02 19:01:01 2020-05-02 19:32:00 20 8 1007 9003 2020-01-02 19:01:01 2020-01-02 19:40:01 89 9 1008 9004 2020-02-02 12:01:01 2020-02-02 12:20:01 99 10 1008 9001 2020-02-02 12:01:01 2020-02-02 12:31:01 98 11 1009 9002 2020-02-02 12:01:01 2020-01-02 12:43:01 81 12 1010 9001 2020-01-02 12:11:01 (NULL) (NULL) 13 1010 9001 2020-02-02 12:01:01 2020-01-02 10:31:01 89 试卷的类别tag可能出现大小写混乱的情况，请先筛选出试卷作答数小于3的类别tag，统计将其转换为大写后对应的原本试卷作答数。 如果转换后tag并没有发生变化，不输出该条结果。 由示例数据结果输出如下： tag answer_cnt C++ 6 解释：被作答过的试卷有9001、9002、9003、9004，他们的tag和被作答次数如下： exam_id tag answer_cnt 9001 算法 4 9002 C++ 6 9003 c++ 2 9004 sql 2 作答次数小于3的tag有c++和sql，而转为大写后只有C++本来就有作答数，于是输出c++转化大写后的作答次数为6。
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_bin;

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, '算法', 'hard', 60, '2020-01-01 10:00:00'),
  (9002, 'C++', 'hard', 80, '2020-01-01 10:00:00'),
  (9003, 'c++', 'hard', 80, '2020-01-01 10:00:00'),
  (9004, 'sql', 'medium', 70, '2020-01-01 10:00:00'),
  (9005, 'C++', 'hard', 80, '2020-01-01 10:00:00'),
  (9006, 'C++', 'hard', 80, '2020-01-01 10:00:00'),
  (9007, 'C++', 'hard', 80, '2020-01-01 10:00:00'),
  (9008, 'SQL', 'medium', 70, '2020-01-01 10:00:00'),
  (9009, 'SQL', 'medium', 70, '2020-01-01 10:00:00'),
  (9010, 'SQL', 'medium', 70, '2020-01-01 10:00:00');
	
INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES
(1001, 9001, '2020-01-01 09:01:01', '2020-01-01 09:21:59', 80),
(1002, 9003, '2020-01-20 10:01:01', '2020-01-20 10:10:01', 81),
(1002, 9002, '2020-01-01 12:11:01', '2020-01-01 12:31:01', 83),
(1003, 9002, '2020-01-01 19:01:01', '2020-01-01 19:30:01', 75),
(1004, 9002, '2020-01-01 12:01:01', '2020-01-01 12:11:01', 60),
(1005, 9002, '2020-01-01 12:01:01', '2020-01-01 12:41:01', 90),
(1006, 9001, '2020-01-02 19:01:01', '2020-01-02 19:32:00', 20),
(1007, 9003, '2020-01-02 19:01:01', '2020-01-02 19:40:01', 89),
(1008, 9004, '2020-01-02 12:01:01', '2020-01-02 12:20:01', 99),
(1008, 9001, '2020-01-02 12:01:01', '2020-01-02 12:31:01', 98),
(1009, 9002, '2020-01-02 12:01:01', '2020-01-02 12:43:01', 81),
(1010, 9002, '2020-01-02 12:11:01', null, null),
(1011, 9001, '2020-01-02 10:01:01', '2020-01-02 10:31:01', 89);

输出

c++|6

备注:
保证数据表创建时已配置了大小写敏感
加载中...