mysql学习--第13章 约束 课后习题

已经存在数据库test04_emp，两张表emp2和dept2

CREATE DATABASE test04_emp;

USE test04_emp;

CREATE TABLE emp2(
id INT,
emp_name VARCHAR(15)
);

CREATE TABLE dept2(
id INT,
dept_name VARCHAR(15)
);

1.向表emp2的id列中添加PRIMARY KEY约束

ALTER TABLE emp2
add PRIMARY KEY(id);

2.向表dept2的id列中添加PRIMARY KEY约束

ALTER TABLE dept2
ADD PRIMARY KEY(id);

3.向表emp2中添加列dept_id，并在其中定义FOREIGN KEY约束，与之相关联的列是dept2表中的id列。

ALTER TABLE emp2
ADD dept_id INT;

DESC emp2;

ALTER TABLE emp2
ADD FOREIGN KEY(dept_id) REFERENCES dept2(id);

练习2：

承接《第11章_数据处理之增删改》的综合案例。

USE test01_library;
DESC books;

根据题目要求给books表中的字段添加约束

方式1：

ALTER TABLE books
ADD PRIMARY KEY(id);

ALTER TABLE books
MODIFY id INT PRIMARY KEY auto_increment;

方式2：

ALTER TABLE books
MODIFY id INT PRIMARY KEY auto_increment;	

DESC books;

针对于非id字段的操作

ALTER table books
MODIFY NAME VARCHAR(50) NOT NULL;

ALTER TABLE books
MODIFY AUTHORS varchar(100) not null;

ALTER TABLE books
MODIFY price FLOAT not null;

ALTER TABLE books
MODIFY pubdate YEAR not null;

ALTER TABLE books
MODIFY num INT not null;

练习3：

1. 创建数据库test04_company

2. 按照下表给出的表结构在test04_company数据库中创建两个数据表offices和employees

CREATE DATABASE IF NOT EXISTS test04_company  CHARACTER set 'utf8';

USE test04_company;

CREATE TABLE if NOT EXISTS offices(
officeCode INT(10) PRIMARY KEY,
city VARCHAR(50) not NULL,
address VARCHAR(50),
country VARCHAR (50) not NULL,
postalCode VARCHAR(15) UNIQUE
);

DESC offices;

CREATE TABLE employees(
employeeNumber INT PRIMARY KEY auto_increment,
lastName VARCHAR(50) not NULL,
fistName VARCHAR(50) not NULL,
mobile VARCHAR(25) UNIQUE,
officeCode int(10) not NULL,
jobTitle VARCHAR(50) NOT NULL,
birth datetime not NULL,
note VARCHAR(255),
sex VARCHAR(5),
CONSTRAINT fk_emp_offcode FOREIGN KEY(officeCode) REFERENCES offices(officeCode)   
);

DESC employees;

3. 将表employees的mobile字段修改到officeCode字段后面

ALTER TABLE employees
MODIFY mobile VARCHAR(25) AFTER officeCode;

4. 将表employees的birth字段改名为employee_birth

ALTER TABLE employees
CHANGE birth employee_birth datetime ;

ALTER TABLE employees
CHANGE  employee_birth  birth datetime NOT NULL;

ALTER TABLE employees
CHANGE birth employee_birth datetime NOT NULL;

5. 修改sex字段，数据类型为CHAR(1)，非空约束

ALTER TABLE employees
MODIFY sex CHAR(1) not NULL;

6. 删除字段note

desc employees;

ALTER TABLE employees
DROP COLUMN note;

7. 增加字段名favoriate_activity，数据类型为VARCHAR(100)

alter TABLE employees
ADD favoriate_activity VARCHAR(100);

8. 将表employees名称修改为employees_info

RENAME TABLE employees
TO employees_info;

#错误：Table 'test04_company.employees' doesn't exist
DESC employees;
DESC employees_info;