SQL增删改操作实例分析

插入记录

SQL1 插入记录（一）

表exam_record结构

 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);

SQL2 插入记录（二）

表exam_record结构

 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_2021SELECT NULL,uid, exam_id, start_time, submit_time, scoreFROM exam_recordWHERE submit_time < '2021-01-01 00:00:00';

SQL3 插入记录（三）

试题信息表examination_info结构

 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');

2 更新记录

SQL4 更新记录（一）

现有一张试卷信息表examination_info，表结构如下图所示：

 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_infoset tag ='Python' WHERE tag='PYTHON';

SQL5 更新记录（二）

作答记录表exam_record表结构

 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_recordset submit_time='2099-01-01 00:00:00',    score=0WHERE start_time<'2021-09-01' and submit_time is null；

3 删除记录

SQL6 删除记录（一）

作答记录表exam_record表结构，start_time是试卷开始时间，submit_time 是交卷，即结束时间

 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_recordwhere timestampdiff(minute,start_time,submit_time) < 5 and score < 60;

SQL7 删除记录（二）

作答记录表exam_record结构如下：

 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，开始作答时间较早的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_recordwhere timestampdiff(minute, start_time, submit_time) < 5or submit_time is nullorder by start_timelimit 3；

SQL8 删除记录（三）

试卷作答记录表exam_record表结构

 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;