当前位置：网站首页>数据库系统原理与应用教程（068）—— MySQL 练习题：操作题 90-94（十二）：DML 语句练习
数据库系统原理与应用教程（068）—— MySQL 练习题：操作题 90-94（十二）：DML 语句练习
2022-07-30 17:26:00 【睿思达DBA_WGX】
数据库系统原理与应用教程（068）—— MySQL 练习题：操作题 90-94（十二）：DML 语句练习
90、创建表
现有一张用户信息表（user_info），表结构如下：
| Filed | Type | Null | Key | Default | Extra | Comment |
|---|---|---|---|---|---|---|
| id | int(11) | NO | PRI | (NULL) | auto_increment | 自增ID |
| uid | int(11) | NO | UNI | (NULL) | 用户ID | |
| nick_name | varchar(64) | YES | (NULL) | 昵称 | ||
| achievement | int(11) | YES | 0 | 成就值 | ||
| level | int(11) | YES | (NULL) | 用户等级 | ||
| job | varchar(32) | YES | (NULL) | 职业方向 | ||
| register_time | datetime | YES | CURRENT_TIMESTAMP | 注册时间 |
【问题】，请创建一张 vip 用户信息表（user_info_vip），表结构和用户信息表一致。
| Filed | Type | Null | Key | Default | Extra | Comment |
|---|---|---|---|---|---|---|
| id | int(11) | NO | PRI | auto_increment | 自增ID | |
| uid | int(11) | NO | UNI | 用户ID | ||
| nick_name | varchar(64) | YES | 昵称 | |||
| achievement | int(11) | YES | 0 | 成就值 | ||
| level | int(11) | YES | 用户等级 | |||
| job | varchar(32) | YES | 职业方向 | |||
| register_time | datetime | YES | CURRENT_TIMESTAMP | 注册时间 |
解答：
/* create table user_info_vip( id int primary key auto_increment comment '自增ID', uid int not null comment '用户ID', nick_name varchar(64) default 0 comment '昵称', achievement int comment '成就值', level int comment '用户等级', job varchar(32) comment '职业方向', register_time datetime default CURRENT_TIMESTAMP comment '注册时间', unique(uid) ) CHARACTER SET utf8 COLLATE utf8_general_ci;; */
mysql> mysql> SHOW FULL FIELDS FROM user_info_vip;
+---------------+-------------+-----------------+------+-----+-------------------+----------------+
| Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment |
+---------------+-------------+-----------------+------+-----+-------------------+----------------+
| id | int(11) | NULL | NO | PRI | NULL | auto_increment | select,insert,update,references | 自增ID |
| uid | int(11) | NULL | NO | UNI | NULL | | select,insert,update,references | 用户ID |
| nick_name | varchar(64) | utf8_general_ci | YES | | 0 | | select,insert,update,references | 昵称 |
| achievement | int(11) | NULL | YES | | NULL | | select,insert,update,references | 成就值 |
| level | int(11) | NULL | YES | | NULL | | select,insert,update,references | 用户等级 |
| job | varchar(32) | utf8_general_ci | YES | | NULL | | select,insert,update,references | 职业方向 |
| register_time | datetime | NULL | YES | | CURRENT_TIMESTAMP | | select,insert,update,references | 注册时间 |
+---------------+-------------+-----------------+------+-----+-------------------+----------------+
7 rows in set (0.00 sec)
91、修改表结构
用户信息表user_info，表结构如下：
| Filed | Type | Null | Key | Default | Extra | Comment |
|---|---|---|---|---|---|---|
| id | int(11) | NO | PRI | (NULL) | auto_increment | 自增ID |
| uid | int(11) | NO | UNI | (NULL) | 用户ID | |
| nick_name | varchar(64) | YES | (NULL) | 昵称 | ||
| achievement | int(11) | YES | 0 | 成就值 | ||
| level | int(11) | YES | (NULL) | 用户等级 | ||
| job | varchar(32) | YES | (NULL) | 职业方向 | ||
| register_time | datetime | YES | CURRENT_TIMESTAMP | 注册时间 |
【问题】请在用户信息表 level 列的后面增加一列，列名为：school，最多可保存 15 个汉字；并将 job 列的列名修改为 profession，同时 varchar 字段长度变为 10；achievement 列的默认值设置为 0。修改之后的结果如下：
| Filed | Type | Null | Key | Default | Extra | Comment |
|---|---|---|---|---|---|---|
| id | int(11) | NO | PRI | auto_increment | 自增ID | |
| uid | int(11) | NO | UNI | 用户ID | ||
| nick_name | varchar(64) | YES | 昵称 | |||
| achievement | int(11) | YES | 0 | |||
| level | int(11) | YES | 用户等级 | |||
| school | varchar(15) | |||||
| profession | varchar(10) | YES | ||||
| register_time | datetime | YES | CURRENT_TIMESTAMP | 注册时间 |
表结构如下：
/* drop table if exists user_info; CREATE TABLE IF NOT EXISTS user_info ( id int PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid int UNIQUE NOT NULL COMMENT '用户ID', `nick_name` varchar(64) COMMENT '昵称', achievement int COMMENT '成就值', level int COMMENT '用户等级', job varchar(10) COMMENT '职业方向', register_time datetime DEFAULT CURRENT_TIMESTAMP COMMENT '注册时间' )CHARACTER SET utf8 COLLATE utf8_general_ci; */
解答：
/* alter table user_info add school varchar(15) after level; alter table user_info change job profession varchar(10); alter table user_info modify achievement int default 0; */
mysql> alter table user_info add school varchar(15) after level;
Query OK, 0 rows affected (0.08 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user_info change job profession varchar(10);
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table user_info modify achievement int default 0;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc user_info;
+---------------+-------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+-------------+------+-----+-------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| uid | int(11) | NO | UNI | NULL | |
| nick_name | varchar(64) | YES | | NULL | |
| achievement | int(11) | YES | | 0 | |
| level | int(11) | YES | | NULL | |
| school | varchar(15) | YES | | NULL | |
| profession | varchar(10) | YES | | NULL | |
| register_time | datetime | YES | | CURRENT_TIMESTAMP | |
+---------------+-------------+------+-----+-------------------+----------------+
8 rows in set (0.00 sec)
92、删除表
现有一张试卷答题记录表：exam_record，一般每年都会为 exam_record 表建立一张备份表 exam_record_{YEAR}，{YEAR}为对应年份。请把很久前的（2011到2014年）备份表都删掉（如果存在的话）。
表结构及数据如下：
/* 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_2010 (LIKE exam_record); CREATE TABLE IF NOT EXISTS exam_record_2012 (LIKE exam_record); CREATE TABLE IF NOT EXISTS exam_record_2013 (LIKE exam_record); CREATE TABLE IF NOT EXISTS exam_record_2014 (LIKE exam_record); CREATE TABLE IF NOT EXISTS exam_record_2015 (LIKE exam_record); */
解答：
mysql> SELECT TABLE_NAME FROM information_schema.TABLES WHERE TABLE_NAME LIKE 'exam_record_201_';
+------------------+
| TABLE_NAME |
+------------------+
| exam_record_2010 |
| exam_record_2012 |
| exam_record_2013 |
| exam_record_2014 |
| exam_record_2015 |
+------------------+
5 rows in set (0.05 sec)
/* drop table if exists exam_record_2011; drop table if exists exam_record_2012; drop table if exists exam_record_2013; drop table if exists exam_record_2014; */
mysql> drop table if exists exam_record_2011;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> drop table if exists exam_record_2012;
Query OK, 0 rows affected (0.00 sec)
mysql> drop table if exists exam_record_2013;
Query OK, 0 rows affected (0.01 sec)
mysql> drop table if exists exam_record_2014;
Query OK, 0 rows affected (0.01 sec)
mysql> SELECT TABLE_NAME FROM information_schema.TABLES WHERE TABLE_NAME LIKE 'exam_record_201_';
+------------------+
| TABLE_NAME |
+------------------+
| exam_record_2010 |
| exam_record_2015 |
+------------------+
2 rows in set (0.00 sec)
93、创建索引
现有一张试卷信息表：examination_info，表结构如下：
| Filed | Type | Null | Key | Default | Extra | Comment |
|---|---|---|---|---|---|---|
| id | int(11) | NO | PRI | NULL | auto_increment | 自增ID |
| exam_id | int(11) | NO | UNI | NULL | 试卷ID | |
| tag | varchar(32) | YES | NULL | 类别标签 | ||
| difficulty | varchar(8) | YES | NULL | 难度 | ||
| duration | int(11) | NO | NULL | 时长 | ||
| release_time | datetime | YES | NULL | 发布时间 |
为了对表更方便快捷地查询，需要在 examination_info 表创建以下索引，规则如下：在 duration 列创建普通索引idx_duration，在 exam_id 列创建唯一性索引 uniq_idx_exam_id、在 tag 列创建全文索引 full_idx_tag。结果如下：
| examination_info | 0 | PRIMARY | 1 | id | A | 0 | BTREE | |||
|---|---|---|---|---|---|---|---|---|---|---|
| examination_info | 0 | uniq_idx_exam_id | 1 | exam_id | A | 0 | YES | BTREE | ||
| examination_info | 1 | idx_duration | 1 | duration | A | 0 | BTREE | |||
| examination_info | 1 | full_idx_tag | 1 | tag | 0 | YES | FULLTEXT |
表结构及数据如下：
/* 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; */
解答：
mysql> SHOW INDEX FROM examination_info;
+------------------+------------+----------+--------------+-------------+-----------+-------------
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality
+------------------+------------+----------+--------------+-------------+-----------+-------------+
| examination_info | 0 | PRIMARY | 1 | id | A | 0 |
| examination_info | 0 | exam_id | 1 | exam_id | A | 0 |
+------------------+------------+----------+--------------+-------------+-----------+-------------+
2 rows in set (0.01 sec)
/* create index dx_duration on examination_info(duration); create unique index uniq_idx_exam_id on examination_info(exam_id); create fulltext index full_idx_tag on examination_info(tag); */
mysql> SHOW INDEX FROM examination_info;
+------------------+------------+------------------+--------------+-------------+-----------+
+| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation |
|+------------------+------------+------------------+--------------+-------------+-----------+
+| examination_info | 0 | PRIMARY | 1 | id | A |
|| examination_info | 0 | exam_id | 1 | exam_id | A |
|| examination_info | 0 | uniq_idx_exam_id | 1 | exam_id | A |
|| examination_info | 1 | dx_duration | 1 | duration | A |
|| examination_info | 1 | full_idx_tag | 1 | tag | NULL |
|+------------------+------------+------------------+--------------+-------------+-----------+
+5 rows in set (0.00 sec)
94、删除索引
【问题】请删除 examination_info 表上的唯一索引 uniq_idx_exam_id 和全文索引 full_idx_tag。
解答：
mysql> SHOW INDEX FROM examination_info;
+------------------+------------+------------------+--------------+-------------+-----------+
+| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation |
|+------------------+------------+------------------+--------------+-------------+-----------+
+| examination_info | 0 | PRIMARY | 1 | id | A |
|| examination_info | 0 | exam_id | 1 | exam_id | A |
|| examination_info | 0 | uniq_idx_exam_id | 1 | exam_id | A |
|| examination_info | 1 | dx_duration | 1 | duration | A |
|| examination_info | 1 | full_idx_tag | 1 | tag | NULL |
|+------------------+------------+------------------+--------------+-------------+-----------+
+5 rows in set (0.00 sec)
/* drop index uniq_idx_exam_id on examination_info; drop index full_idx_tag on examination_info; */
mysql> drop index uniq_idx_exam_id on examination_info;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> drop index full_idx_tag on examination_info;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> SHOW INDEX FROM examination_info;
+------------------+------------+-------------+--------------+-------------+-----------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation |
+------------------+------------+-------------+--------------+-------------+-----------+
| examination_info | 0 | PRIMARY | 1 | id | A |
| examination_info | 0 | exam_id | 1 | exam_id | A |
| examination_info | 1 | dx_duration | 1 | duration | A |
+------------------+------------+-------------+--------------+-------------+-----------+
3 rows in set (0.00 sec)
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