(简答题)

1、按照结构表提示在数据库中创建数据表，要求使用SQL 语句实现。

2、按照下列要求完成操作，要求使用SQL 语句实现。

(1) 为读者表 reader 指定检査约束，即指定性别 sex 字段的值只能是“男”或“女”。

(2) 修改读者表reader 的默认值约束，使读者类别 typeno 字段的默认值为“1”。

(3) 为图书表 book 指定检査约束，即指定定价 price 字段的值必须大于 0。

<1>创建数据库，进入数据库

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| t2                 |
+--------------------+
5 rows in set (0.00 sec)mysql> create database test;
Query OK, 1 row affected (0.00 sec)mysql> use test;
Database changed
mysql>

 <2>创建数据库 reader 表

mysql>  create table reader(rid char(12) NOT NULL PRIMARY KEY comment '读者编号',->  mame varchar(50) comment '读者姓名',->  sex char(1) comment '性别',->  typeno char(1) DEFAULT '2' comment '读者类别',->  dept varchar(50)  comment '所属院系',->  tel varchar(50) comment '联系电话');
Query OK, 0 rows affected (0.01 sec)mysql> desc reader;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| rid    | char(12)    | NO   | PRI | NULL    |       |
| mame   | varchar(50) | YES  |     | NULL    |       |
| sex    | char(1)     | YES  |     | NULL    |       |
| typeno | char(1)     | YES  |     | 2       |       |
| dept   | varchar(50) | YES  |     | NULL    |       |
| tel    | varchar(50) | YES  |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

插入几组数据看看

mysql> insert into reader(rid,mame,sex,dept,tel) values ('1',"东方暮雪",'男',"计算机","13766269172");
Query OK, 1 row affected (0.00 sec)mysql> insert into reader(rid,mame,sex,dept,tel) values ('2',"东方初晴",'女',"计算机","12345678901");
Query OK, 1 row affected (0.00 sec)mysql> select * from reader;
+-----+--------------+------+--------+-----------+-------------+
| rid | mame         | sex  | typeno | dept      | tel         |
+-----+--------------+------+--------+-----------+-------------+
| 1   | 东方暮雪     | 男   | 2      | 计算机    | 13766269172 |
| 2   | 东方初晴     | 女   | 2      | 计算机    | 12345678901 |
+-----+--------------+------+--------+-----------+-------------+
2 rows in set (0.00 sec)

完美 ~

<3>现在创建另一张表 book

mysql> create table book(bid char(8)  NOT NULL PRIMARY KEY comment '图书编号',-> bname varchar(50) comment '书名',-> author varchar(50) comment '作者',-> publisher varchar(50) comment '出版社',-> publishdate date comment '出版日期',-> price float comment '定价',-> total int comment '库存数量',-> position varchar(50) comment '存放位置');
Query OK, 0 rows affected (0.01 sec)mysql> desc book;
+-------------+-------------+------+-----+---------+-------+
| Field       | Type        | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+-------+
| bid         | char(8)     | NO   | PRI | NULL    |       |
| bname       | varchar(50) | YES  |     | NULL    |       |
| author      | varchar(50) | YES  |     | NULL    |       |
| publisher   | varchar(50) | YES  |     | NULL    |       |
| publishdate | date        | YES  |     | NULL    |       |
| price       | float       | YES  |     | NULL    |       |
| total       | int(11)     | YES  |     | NULL    |       |
| position    | varchar(50) | YES  |     | NULL    |       |
+-------------+-------------+------+-----+---------+-------+
8 rows in set (0.00 sec)

插入几组数据看看

mysql> insert into book values ('1',"诗经","孔子","东方出版社",'2024-9-10',9.9,35,"鲁国");
Query OK, 1 row affected (0.00 sec)mysql> insert into book values ('2',"楚辞","屈原","东方出版社",'2024-9-11',9.9,35,"楚国");
Query OK, 1 row affected (0.00 sec)mysql> select * from book;
+-----+--------+--------+-----------------+-------------+-------+-------+----------+
| bid | bname  | author | publisher       | publishdate | price | total | position |
+-----+--------+--------+-----------------+-------------+-------+-------+----------+
| 1   | 诗经   | 孔子   | 东方出版社      | 2024-09-10  |   9.9 |    35 | 鲁国     |
| 2   | 楚辞   | 屈原   | 东方出版社      | 2024-09-11  |   9.9 |    35 | 楚国     |
+-----+--------+--------+-----------------+-------------+-------+-------+----------+
2 rows in set (0.00 sec)

现在我们第一题已经完成了，现在就是按照题目要求去添加约束

<4>

(1)为读者表 reader 指定检査约束，即指定性别 sex 字段的值只能是“男”或“女”。

mysql>  alter table reader ADD CONSTRAINT check (sex ='男' or sex='女');
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

(2)修改读者表reader 的默认值约束，使读者类别 typeno 字段的默认值为“1”。

mysql> alter table reader MODIFY COLUMN typeno char(1) DEFAULT '1';
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0mysql>  desc reader;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| rid    | char(12)    | NO   | PRI | NULL    |       |
| mame   | varchar(50) | YES  |     | NULL    |       |
| sex    | char(1)     | YES  |     | NULL    |       |
| typeno | char(1)     | YES  |     | 1       |       |
| dept   | varchar(50) | YES  |     | NULL    |       |
| tel    | varchar(50) | YES  |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

(3)为图书表 book 指定检査约束，即指定定价 price 字段的值必须大于 0。

mysql> alter table book ADD CONSTRAINT check (price>0);
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0