数据库管理
1. 查看数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| test |
+--------------------+
3 rows in set (0.06 sec)
说明： information_schema保存系统云信息
mysql 保存系统授权表
tesst 是测试数据库
2. 选择数据库
mysql> use test
Database changed
3. 创建数据库
mysql> create database techdb;
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| techdb |
| test |
+--------------------+
4 rows in set (0.00 sec)
[root@demoserver bin]# find / -name techdb
/var/lib/mysql/techdb
备注： 数据库创建完成后，会在/var/lib/mysql/下创建一个相同文件夹，用于保存数据库文件，如上述所示。
数据库结构管理
1. 数据表结构
数据库中的数据以二维表形式保存在数据表中，每行代表一个记录，每条记录包含多个列，每列表示一个字段。
--使用information_sechema数据库
mysql> use information_sechema
--显示使用information_sechema数据库下所有表
mysql> show tables
-> ;
+---------------------------------------+
| Tables_in_information_schema |
+---------------------------------------+
| CHARACTER_SETS |
| COLLATIONS |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS |
| COLUMN_PRIVILEGES |
| KEY_COLUMN_USAGE |
| PROFILING |
| ROUTINES |
| SCHEMATA |
| SCHEMA_PRIVILEGES |
| STATISTICS |
| TABLES |
| TABLE_CONSTRAINTS |
| TABLE_PRIVILEGES |
| TRIGGERS |
| USER_PRIVILEGES |
| VIEWS |
+---------------------------------------+
17 rows in set (0.00 sec)
--显示CHARACTER_SETS表的结构
mysql> describe CHARACTER_SETS;
+----------------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------------+-------------+------+-----+---------+-------+
| CHARACTER_SET_NAME | varchar(64) | NO | | | |
| DEFAULT_COLLATE_NAME | varchar(64) | NO | | | |
| DESCRIPTION | varchar(60) | NO | | | |
| MAXLEN | bigint(3) | NO | | 0 | |
+----------------------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
2. 创建数据库表
--新建表
create table employees(
emp_id varchar(10) primary key not null,
first_name varchar(10) not null,
last_name varchar(10) not null,
hire_date date,
job_id int not null,
salary int default 0,
manager_id int ,
dept_id int not null
)
--linux下执行该表
mysql> create table employees(
->
-> emp_id varchar(10) primary key not null,
-> first_name varchar(10) not null,
-> last_name varchar(10) not null,
-> hire_date date,
-> job_id int not null,
-> salary int default 0,
-> manager_id int ,
-> dept_id int not null
-> )
-> ;
Query OK, 0 rows affected (0.03 sec)
--显示表的结构
mysql> describe employees;
+------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| emp_id | varchar(10) | NO | PRI | | |
| first_name | varchar(10) | NO | | | |
| last_name | varchar(10) | NO | | | |
| hire_date | date | YES | | NULL | |
| job_id | int(11) | NO | | | |
| salary | int(11) | YES | | 0 | |
| manager_id | int(11) | YES | | NULL | |
| dept_id | int(11) | NO | | | |
+------------+-------------+------+-----+---------+-------+
8 rows in set (0.00 sec)
3. 更改表结构
--添加字段
mysql> alter table employees add telphone char(20);
mysql> describe employees;
+------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| emp_id | varchar(10) | NO | PRI | | |
| first_name | varchar(10) | NO | | | |
| last_name | varchar(10) | NO | | | |
| hire_date | date | YES | | NULL | |
| job_id | int(11) | NO | | | |
| salary | int(11) | YES | | 0 | |
| manager_id | int(11) | YES | | NULL | |
| dept_id | int(11) | NO | | | |
| telphone | char(20) | YES | | NULL | |
+------------+-------------+------+-----+---------+-------+
--更改字段：更改employees表中的telphone为tel，可以使用change命令
mysql> alter table employees change telphone tel char(20);
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> describe employees;
+------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| emp_id | varchar(10) | NO | PRI | | |
| first_name | varchar(10) | NO | | | |
| last_name | varchar(10) | NO | | | |
| hire_date | date | YES | | NULL | |
| job_id | int(11) | NO | | | |
| salary | int(11) | YES | | 0 | |
| manager_id | int(11) | YES | | NULL | |
| dept_id | int(11) | NO | | | |
| tel | char(20) | YES | | NULL | |
+------------+-------------+------+-----+---------+-------+
9 rows in set (0.00 sec)
--更改字段tel类型：使用modify命令即可。
mysql> alter table employees modify tel varchar(20);
mysql> describe employees;
+------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| emp_id | varchar(10) | NO | PRI | | |
| first_name | varchar(10) | NO | | | |
| last_name | varchar(10) | NO | | | |
| hire_date | date | YES | | NULL | |
| job_id | int(11) | NO | | | |
| salary | int(11) | YES | | 0 | |
| manager_id | int(11) | YES | | NULL | |
| dept_id | int(11) | NO | | | |
| tel | varchar(20) | YES | | NULL | |
+------------+-------------+------+-----+---------+-------+
--删除字段
mysql> alter table employees drop tel;
mysql> describe employees;
+------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| emp_id | varchar(10) | NO | PRI | | |
| first_name | varchar(10) | NO | | | |
| last_name | varchar(10) | NO | | | |
| hire_date | date | YES | | NULL | |
| job_id | int(11) | NO | | | |
| salary | int(11) | YES | | 0 | |
| manager_id | int(11) | YES | | NULL | |
| dept_id | int(11) | NO | | | |
+------------+-------------+------+-----+---------+-------+
4. 插入表数据
mysql> insert into employees(emp_id,first_name,last_name,job_id,dept_id) values(100000,'shen','Fuli',1000,100000);
mysql> insert into employees(emp_id,first_name,last_name,hire_date,job_id,dept_id) values(100001,'zhang','san',now(),1001,100001);
Query OK, 1 row affected (0.00 sec)
5. 查询数据库表
mysql> select * from employees;
+--------+------------+-----------+------------+--------+--------+------------+---------+
| emp_id | first_name | last_name | hire_date | job_id | salary | manager_id | dept_id |
+--------+------------+-----------+------------+--------+--------+------------+---------+
| 100000 | shen | Fuli | NULL | 1000 | 0 | NULL | 100000 |
| 100001 | zhang | san | 2013-06-02 | 1001 | 0 | NULL | 100001 |
+--------+------------+-----------+------------+--------+--------+------------+---------+
6.复制数据表
--仅复制数据结构
mysql> create table employees1 like employees;
Query OK, 0 rows affected (0.01 sec)
mysql> create table employees2 as select * from employees;
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
--复制表结构和数据
mysql> create table employees2 as select * from employees;
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from employees2;
+--------+------------+-----------+------------+--------+--------+------------+---------+
| emp_id | first_name | last_name | hire_date | job_id | salary | manager_id | dept_id |
+--------+------------+-----------+------------+--------+--------+------------+---------+
| 100000 | shen | Fuli | NULL | 1000 | 0 | NULL | 100000 |
| 100001 | zhang | san | 2013-06-02 | 1001 | 0 | NULL | 100001 |
+--------+------------+-----------+------------+--------+--------+------------+---------+
2 rows in set (0.00 sec)
