第10章_创建和管理表的课后练习

#练习1：
#1. 创建数据库test01_office,指明字符集为utf8。并在此数据库下执行下述操作

CREATE DATABASE IF NOT EXISTS test01_office CHARACTER SET 'utf8';

USE test01_office;

#2. 创建表dept01
/*
字段 类型
id INT(7)
NAME VARCHAR(25)
*/
CREATE TABLE IF NOT EXISTS dept01(
id INT(7),
name VARCHAR(25)
);

#3.将表departments中的数据插入新表dept02中
CREATE TABLE dept02
AS
SELECT *
FROM atguigudb.departments;

#4. 创建表emp01
/*
字段 类型
id INT(7)
first_name VARCHAR (25)
last_name VARCHAR(25)
dept_id INT(7)
*/

CREATE TABLE emp01(
id INT(7),
first_name VARCHAR(25),
last_name VARCHAR(25),
dept_id INT(7)
);

#5.将列last_name的长度增加到50
DESC emp01;

ALTER TABLE emp01
MODIFY last_name VARCHAR(50);

#6.根据表employees创建emp02
CREATE TABLE emp02
AS
SELECT *
FROM atguigudb.employees;

SHOW TABLES FROM test01_office;

#7.删除表emp01
DROP TABLE emp01;

#8.将表emp02重命名为emp01
#alter table emp02 rename to emp01;
RENAME TABLE emp02 TO emp01;

#9.在表dept02和emp01中添加新列test_column，并检查所作的操作
ALTER TABLE emp01 ADD test_column VARCHAR(10);

DESC emp01;

ALTER TABLE dept02 ADD test_column VARCHAR(10);

DESC dept02;

#10.直接删除表emp01中的列 department_id

ALTER TABLE emp01
DROP COLUMN department_id;

#练习2：

1、创建数据库 test02_market

CREATE DATABASE IF NOT EXISTS test02_market CHARACTER SET 'utf8';

USE test02_market;

SHOW CREATE DATABASE test02_market;

2、创建数据表 customers

CREATE TABLE IF NOT EXISTS customers(
c_num INT,
c_name VARCHAR(50),
c_contact VARCHAR(50),
c_city VARCHAR(50),
c_birth DATE
);

SHOW TABLES;

3、将 c_contact 字段移动到 c_birth 字段后面

DESC customers;

ALTER TABLE customers
MODIFY c_contact VARCHAR(50) AFTER c_birth;

4、将 c_name 字段数据类型改为 varchar(70)

ALTER TABLE customers
MODIFY c_name VARCHAR(70) ;

5、将c_contact字段改名为c_phone

ALTER TABLE customers
CHANGE c_contact c_phone VARCHAR(50);

6、增加c_gender字段到c_name后面，数据类型为char(1)

ALTER TABLE customers
ADD c_gender CHAR(1) AFTER c_name;

7、将表名改为customers_info

RENAME TABLE customers
TO customers_info;

DESC customers_info;

8、删除字段c_city

ALTER TABLE customers_info
DROP COLUMN c_city;

#练习3：

1、创建数据库test03_company

CREATE DATABASE IF NOT EXISTS test03_company CHARACTER SET 'utf8';

USE test03_company;

2、创建表offices

CREATE TABLE IF NOT EXISTS offices(
officeCode INT,
city VARCHAR(30),
address VARCHAR(50),
country VARCHAR(50),
postalCode VARCHAR(25)
);

DESC offices;

3、创建表employees

CREATE TABLE IF NOT EXISTS employees(
empNum INT,
lastName VARCHAR(50),
firstName VARCHAR(50),
mobile VARCHAR(25),
code INT,
jobTitle VARCHAR(50),
birth DATE,
note VARCHAR(255),
sex VARCHAR(5)

);

DESC employees;

4、将表employees的mobile字段修改到code字段后面

ALTER TABLE employees
MODIFY mobile VARCHAR(20) AFTER code;

5、将表employees的birth字段改名为birthday

ALTER TABLE employees
CHANGE birth birthday DATE;

6、修改sex字段，数据类型为char(1)

ALTER TABLE employees
MODIFY sex CHAR(1);

7、删除字段note

ALTER TABLE employees
DROP COLUMN note;

8、增加字段名favoriate_activity，数据类型为varchar(100)

ALTER TABLE employees
ADD favoriate_activity VARCHAR(100);

9、将表employees的名称修改为 employees_info

RENAME TABLE employees TO employees_info;

DESC employees_info;