Detailed introduction to SQL addition, deletion and modification operations

题目描述 牛客后台会记录每个用户的试卷作答记录到exam_record表，现在有两个用户的作答记录详情如下： 用户1001在2021年9月1日晚上10点11分12秒开始作答试卷9001，并在50分钟后提交，得了90分； 用户1002在2021年9月4日上午7点1分2秒开始作答试卷9002，并在10分钟后退出了平台。 试卷作答记录表exam_record中，表已建好，其结构如下，请用一条语句将这两条记录插入表中。 该题最后会通过执行SELECT uid, exam_id, start_time, submit_time, score FROM exam_record; 来对比结果 建表语句 drop table if EXISTS exam_record; CREATE TABLE IF NOT EXISTS 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; TRUNCATE exam_record; 答案 insert INTO exam_record values(null,1001,9001,'2021-09-01 22:11:12','2021-09-01 23:01:12',90), (null,1002,9002,'2021-09-04 07:01:02',null,null);

题目描述 现有一张试卷作答记录表exam_record，其中包含多年来的用户作答试卷记录， 由于数据越来越多，维护难度越来越大，需要对数据表内容做精简，历史数据做备份。 我们已经创建了一张新表exam_record_before_2021用来备份2021年之前的试题作答记录， 结构和exam_record表一致，请将2021年之前的已完成了的试题作答纪录导入到该表。 后台会通过执行"SELECT * FROM exam_record_before_2021;"语句来对比结果 建表语句 drop table if EXISTS exam_record; CREATE TABLE IF NOT EXISTS 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; CREATE TABLE IF NOT EXISTS exam_record_before_2021 ( 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; TRUNCATE exam_record; TRUNCATE exam_record_before_2021; INSERT INTO exam_record(uid,exam_id,start_time,submit_time,score) VALUES (1001, 9001, '2020-01-01 09:00:01', null, null), (1001, 9002, '2020-01-02 09:01:01', '2020-01-02 09:21:01', 70), (1001, 9002, '2020-09-02 09:00:01', null, null), (1002, 9001, '2021-05-02 10:01:01', '2021-05-02 10:30:01', 81), (1002, 9002, '2021-09-02 12:01:01', null, null); 答案 INSERT INTO exam_record_before_2021 SELECT NULL,uid, exam_id, start_time, submit_time, score FROM exam_record WHERE submit_time 
## SQL3 insert record (3)
 Examination information table examination_info Structure

 题目描述 现在有一套ID为9003的高难度SQL试卷，时长为一个半小时， 请你将 2021-01-01 00:00:00 作为发布时间插入到试题信息表examination_info，不管该ID试卷是否存在，都要插入成功，请尝试插入它。 后台会通过执行 SELECT exam_id,tag,difficulty,duration,release_time FROM examination_info 语句来对比结果。 建表语句 drop table if EXISTS examination_info; CREATE TABLE IF NOT EXISTS 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(分钟数)', release_time datetime COMMENT '发布时间' )CHARACTER SET utf8 COLLATE utf8_bin; TRUNCATE examination_info; INSERT INTO examination_info(exam_id,tag,difficulty,duration,release_time) VALUES (9001, 'SQL', 'hard', 60, '2020-01-01 10:00:00'), (9002, '算法', 'easy', 60, '2020-01-01 10:00:00'), (9003, 'SQL', 'medium', 60, '2020-01-02 10:00:00'), (9004, '算法', 'hard', 80, '2020-01-01 10:00:00'); 答案 replace into examination_info (id,exam_id,tag,difficulty,duration,release_time) values(null,9003,'SQL','hard',90,'2021-01-01 00:00:00');
        

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题目描述 请把examination_info表中tag为PYTHON的tag字段全部修改为Python。 后台会通过执行'SELECT exam_id,tag,difficulty,duration,release_time FROM examination_info;'语句来对比结果。 建表语句 drop table if EXISTS examination_info; CREATE TABLE IF NOT EXISTS 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; TRUNCATE examination_info; INSERT INTO examination_info(exam_id,tag,difficulty,duration,release_time) VALUES (9001, 'SQL', 'hard', 60, '2020-01-01 10:00:00'), (9002, 'python', 'easy', 60, '2020-01-01 10:00:00'), (9003, 'Python', 'medium', 80, '2020-01-01 10:00:00'), (9004, 'PYTHON', 'hard', 80, '2020-01-01 10:00:00'); 答案 UPDATE examination_info set tag ='Python' WHERE tag='PYTHON';

题目描述 现有一张试卷作答记录表exam_record，其中包含多年来的用户作答试卷记录,submit_time为 完成时间 请把exam_record表中2021年9月1日之前开始作答的未完成记录全部改为被动完成， 即：将完成时间改为'2099-01-01 00:00:00'，分数改为0。 建表语句 drop table if EXISTS exam_record; CREATE TABLE IF NOT EXISTS 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 exam_record(uid,exam_id,start_time,submit_time,score) VALUES (1001, 9001, '2020-01-02 09:01:01', '2020-01-02 09:21:01', 80), (1001, 9002, '2021-09-01 09:01:01', '2021-09-01 09:21:01', 90), (1002, 9001, '2021-08-02 19:01:01', null, null), (1002, 9002, '2021-09-05 19:01:01', '2021-09-05 19:40:01', 89), (1003, 9001, '2021-09-02 12:01:01', null, null), (1003, 9002, '2021-09-01 12:01:01', null, null); 答案 UPDATE exam_record set submit_time='2099-01-01 00:00:00', score=0 WHERE start_time
3 Delete record
  SQL6 Delete records (1) 
 Answer record table exam_record table structure, start_time is the start time of the test paper, submit_time is the hand-in time, that is, the end time
 题目描述 现有一张试卷作答记录表exam_record，其中包含多年来的用户作答试卷记录， start_time是试卷开始时间 submit_time 是交卷，即结束时间 请删除exam_record表中作答时间小于5分钟整且分数不及格（及格线为60分）的记录； 后台会执行您的SQL，然后通过 SELECT * FROM exam_record; 语句来筛选出剩下的数据，与正确数据进行对比。 建表语句 drop table if EXISTS exam_record; CREATE TABLE IF NOT EXISTS 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; TRUNCATE exam_record; INSERT INTO exam_record(uid, exam_id, start_time, submit_time, score) VALUES (1001, 9001, '2020-01-01 22:11:12', '2020-01-01 23:16:12', 50), (1001, 9002, '2020-01-02 09:01:01', '2020-01-02 09:06:00', 58), (1002, 9001, '2021-05-02 10:01:01', '2021-05-02 10:05:58', 60), (1002, 9002, '2021-06-02 19:01:01', '2021-06-02 19:05:01', 54), (1003, 9001, '2021-09-05 19:01:01', '2021-09-05 19:40:01', 49), (1003, 9001, '2021-09-05 19:01:01', '2021-09-05 19:15:01', 70), (1003, 9001, '2021-09-06 19:01:01', '2021-09-06 19:05:01', 80), (1003, 9002, '2021-09-09 07:01:02', null, null); 答案 delete from exam_record where timestampdiff(minute,start_time,submit_time) 
 SQL7 Delete Records (2)
 The answer record table exam_record has the following structure: 
 题目描述 现有一张试卷作答记录表exam_record，其中包含多年来的用户作答试卷记录，start_time是试卷开始时间 submit_time 是交卷时间，即结束时间，如果未完成的话，则为空 请删除exam_record表中未完成作答或作答时间小于5分钟整的记录中，开始作答时间最早的3条记录。 后台会通过 SELECT * FROM exam_record 语句来对比结果。 建表语句 drop table if EXISTS exam_record; CREATE TABLE IF NOT EXISTS 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; TRUNCATE exam_record; INSERT INTO exam_record(uid, exam_id, start_time, submit_time, score) VALUES (1001, 9001, '2020-01-01 22:11:12', '2020-01-01 23:16:12', 50), (1001, 9002, '2020-01-02 09:01:01', '2020-01-02 09:06:00', 58), (1001, 9002, '2020-01-02 09:01:01', '2020-01-02 09:05:01', 58), (1002, 9001, '2021-05-02 10:01:01', '2021-05-02 10:06:58', 60), (1002, 9002, '2021-06-02 19:01:01', null, null), (1003, 9001, '2021-09-05 19:01:01', null, null), (1003, 9001, '2021-09-05 19:01:01', null, null), (1003, 9002, '2021-09-09 07:01:02', null, null); 答案 delete from exam_record where timestampdiff(minute, start_time, submit_time) 
 SQL8 Delete records (3) 
 Exam_record table structure of exam paper answer record table 
 题目描述 现有一张试卷作答记录表exam_record，其中包含多年来的用户作答试卷记录， 请删除exam_record表中所有记录，并重置自增主键。 后台会通过SELECT table_rows, auto_increment FROM information_schema.tables WHERE table_name='exam_record'语句来对比输出结果 建表语句 drop table if EXISTS exam_record; CREATE TABLE IF NOT EXISTS 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; TRUNCATE exam_record; INSERT INTO exam_record(uid, exam_id, start_time, submit_time, score) VALUES (1001, 9001, '2020-01-01 22:11:12', '2020-01-01 23:16:12', 50), (1001, 9002, '2020-01-02 09:01:01', '2020-01-02 09:06:00', 58); 答案 TRUNCATE table exam_record;
        

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