目录
三、数据库的基本操作
1.数据库中库的操作
①创建数据库
②字符集和校验规则
③操纵数据库
④备份与恢复
2.数据库中表的操作
①创建表
②查看表
1> 查看表位于的数据库
2>查看所有表
3>查看表中的数据
4>查看创建表的时候的详细信息
③修改表
1>修改表的名字
2>修改表的内容，插入数据
3>修改表的Type属性
4>修改表的Field属性
5>删除表中某一列
④删除表
三、数据库的基本操作
1.数据库中库的操作
①创建数据库
CREATE DATABASE database_name; -- 最基本的写法
CREATE [IF NOT EXISTS] DATABASE data
CHARACTER SET 'utf8mb4' -- 指定字符集
COLLATE 'utf8mb4_unicode_ci'; -- 指定校验规则
[IF NOT EXISTS] -- 可选项，表示如果不存在就创建
说明：当我们创建数据库没有指定字符集和校验规则时
系统使用默认字符集：u8
校验规则是：utf8_general_ci
创建一个使用utf8字符集的db2数据库
create database db2 charset=utf8;
创建一个使用utf8字符集，并带校对规则的db3数据库。
create database db3 charset=utf8 collate utf8_general_ci;
②字符集和校验规则
-- 查看系统默认字符集以及校验规则
show variables like 'character_set_database';
show variables like 'collation_database';
-- 查看数据库支持的字符集
show charset;
-- 查看数据库支持的字符集校验规则
show collation;校验规则对数据库的影响：
- 使用
utf8_general_ci校验规则
mysql> create database test1 collate utf8_general_ci;
Query OK, 1 row affected (0.00 sec)
mysql> use test1;
Database changed
mysql> create table person(name varchar(20));
Query OK, 0 rows affected (0.01 sec)
mysql> insert into person values('a');
Query OK, 1 row affected (0.00 sec)
mysql> insert into person values('A');
Query OK, 1 row affected (0.00 sec)
mysql> insert into person values('b');
Query OK, 1 row affected (0.01 sec)
mysql> insert into person values('B');
Query OK, 1 row affected (0.01 sec)
- 使用
utf8_bin校验规则
mysql> create database test2 collate utf8_bin;
Query OK, 1 row affected (0.00 sec)
mysql> use test2;
Database changed
mysql> create table person(name varchar(20));
Query OK, 0 rows affected (0.02 sec)
mysql> insert into person values('a');
Query OK, 1 row affected (0.00 sec)
mysql> insert into person values('A');
Query OK, 1 row affected (0.00 sec)
mysql> insert into person values('b');
Query OK, 1 row affected (0.01 sec)
mysql> insert into person values('B');
Query OK, 1 row affected (0.00 sec)- 查询
-- utf8_general_ci
mysql> use test1;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select * from person where name='a';
+------+
| name |
+------+
| a |
| A |
+------+
2 rows in set (0.00 sec)
-- utf8_bin
mysql> use test2;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select * from person where name='a';
+------+
| name |
+------+
| a |
+------+
1 row in set (0.00 sec)
- 结果排序
-- utf8_general_ci
mysql> use test1;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select * from person order by name;
+------+
| name |
+------+
| a |
| A |
| b |
| B |
+------+
4 rows in set (0.00 sec)
-- utf8_bin
mysql> use test2;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select * from person order by name;
+------+
| name |
+------+
| A |
| B |
| a |
| b |
+------+
4 rows in set (0.00 sec)
-- utf8_general_ci 不区分大小写
-- utf8_bin 区分大小写
不同的校验规则在进行数据库操作的时候会产生不同的结果
③操纵数据库
-- 查看数据库
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| bookstore |
| helloworld |
| mysql |
| performance_schema |
| sys |
| test1 |
| test2 |
+--------------------+
8 rows in set (0.00 sec)
-- 显示创建数据库语句
mysql> show create database test1;
+----------+----------------------------------------------------------------+
| Database | Create Database |
+----------+----------------------------------------------------------------+
| test1 | CREATE DATABASE `test1` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+----------------------------------------------------------------+
1 row in set (0.00 sec)
-- 修改数据库，将 mytest 数据库字符集改成 gbk
mysql> alter database test1 charset=gbk;
Query OK, 1 row affected (0.00 sec)
mysql> show create database test1;
+----------+---------------------------------------------------------------+
| Database | Create Database |
+----------+---------------------------------------------------------------+
| test1 | CREATE DATABASE `test1` /*!40100 DEFAULT CHARACTER SET gbk */ |
+----------+---------------------------------------------------------------+
1 row in set (0.00 sec)
-- 删除数据库
mysql> DROP database test1;
Query OK, 1 row affected (0.01 sec)
④备份与恢复
1. 备份
mysqldump -P3306 -u root -p 密码 -B 数据库名 > 数据库备份存储的文件路径
-- 示例：将mytest库备份到文件（退出连接）
mysqldump -P3306 -u root -p123456 -B mytest > D:/mytest.sql
-- 这时，可以打开看看 mytest.sql 文件里的内容，其实把我们整个创建数据库，建表，导入数据的语句
都装载这个文件中。2. 还原
source 备份数据库的路径
mysql> source D:/mysql-5.7.22/mytest.sql;3. 备份一张表
mysqldump -u root -p 数据库名 表名1 表名2 > D:/mytest.sql4. 同时备份多个数据库
mysqldump -u root -p -B 数据库名1 数据库名2 ... > 数据库存放路径如果备份一个数据库时，没有带上-B参数，在恢复数据库时，需要先创建空数据库，然后使用数据库，再使用source来还原。
5. 查看数据库连接情况
mysql> show processlist;
+----+------+-----------+------+---------+------+----------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+------+-----------+------+---------+------+----------+------------------+
| 15 | root | localhost | NULL | Query | 0 | starting | show processlist |
+----+------+-----------+------+---------+------+----------+------------------+
1 row in set (0.00 sec)
2.数据库中表的操作
①创建表
mysql> create database user_db;
Query OK, 1 row affected (0.00 sec)
mysql> use user_db;
Database changed
-- 两张表使用不同的存储引擎，user1使用MyIsam，user2使用InnoDB
mysql> create table user1(
-> id int,
-> name varchar(20) comment '用户名',
-> password char(32) comment '用户密码',
-> birthday date comment '用户生日'
-> )character set utf8 collate utf8_general_ci engine MyIsam;
Query OK, 0 rows affected (0.00 sec)
mysql> create table user2(
-> id int,
-> name varchar(20) comment '用户名',
-> password char(32) comment '用户密码',
-> birthday date comment '用户生日'
-> )character set utf8 collate utf8_general_ci engine InnoDB;
Query OK, 0 rows affected (0.01 sec)
因为使用不同的存储引擎，所以表结构不同
如果直接创建而不制定存储引擎：
mysql> create table user3(name char(32));
Query OK, 0 rows affected (0.02 sec)
因为在配置mysql的时候配置了默认的存储引擎（vim /etc/my.cnf查看配置）
②查看表
1> 查看表位于的数据库
-- 查看当前位于的数据库
mysql> select database();
+------------+
| database() |
+------------+
| user_db |
+------------+
1 row in set (0.00 sec)
2>查看所有表
-- 查看所有表
mysql> show tables;
+-------------------+
| Tables_in_user_db |
+-------------------+
| user1 |
| user2 |
| user3 |
+-------------------+
3 rows in set (0.00 sec)3>查看表中的数据
-- 查看表中的数据
mysql> desc user1;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| password | char(32) | YES | | NULL | |
| birthday | date | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
mysql> desc user2;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| password | char(32) | YES | | NULL | |
| birthday | date | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
mysql> desc user3;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| name | char(32) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
1 row in set (0.00 sec)
4>查看创建表的时候的详细信息
-- 查看创建表的时候的详细信息
mysql> show create table user1 \G
*************************** 1. row ***************************
Table: user1
Create Table: CREATE TABLE `user1` (
`id` int(11) DEFAULT NULL,
`name` varchar(20) DEFAULT NULL COMMENT '用户名',
`password` char(32) DEFAULT NULL COMMENT '用户密码',
`birthday` date DEFAULT NULL COMMENT '用户生日'
) ENGINE=MyISAM DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
③修改表
1>修改表的名字
-- 显示当前表信息
mysql> desc user1;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| password | char(32) | YES | | NULL | |
| birthday | date | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
-- 更改表的名字
mysql> alter table user1 rename to user;
Query OK, 0 rows affected (0.00 sec)
-- 显示更改后的表的名字
mysql> show tables;
+-------------------+
| Tables_in_user_db |
+-------------------+
| user |
+-------------------+
1 row in set (0.00 sec)
2>修改表的内容，插入数据
-- 显示表的信息
mysql> desc user;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| password | char(32) | YES | | NULL | |
| birthday | date | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
-- 向表中插入第一条数据
mysql> insert into user values(1,'张三','12345','2010-10-1');
Query OK, 1 row affected (0.00 sec)
-- 向表中插入第二条数据
mysql> insert into user values(1,'李四','23456','2015-1-1');
Query OK, 1 row affected (0.00 sec)
-- 查询表中所有内容
mysql> select * from user;
+------+--------+----------+------------+
| id | name | password | birthday |
+------+--------+----------+------------+
| 1 | 张三 | 12345 | 2010-10-01 |
| 1 | 李四 | 23456 | 2015-01-01 |
+------+--------+----------+------------+
2 rows in set (0.00 sec)
-- 新增一列，且在birthday一列之后
mysql> alter table user add image_path varchar(128) comment '用户的头像路径' after birthday;
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from user;
+------+--------+----------+------------+------------+
| id | name | password | birthday | image_path |
+------+--------+----------+------------+------------+
| 1 | 张三 | 12345 | 2010-10-01 | NULL |
| 1 | 李四 | 23456 | 2015-01-01 | NULL |
+------+--------+----------+------------+------------+
2 rows in set (0.00 sec)3>修改表的Type属性
-- 当前表的属性
mysql> desc user;
+------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| password | char(32) | YES | | NULL | |
| birthday | date | YES | | NULL | |
| image_path | varchar(128) | YES | | NULL | |
+------------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
-- 修改某一属性，如name的Type
mysql> alter table user modify name varchar(60);
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
-- 查看修改后的表的属性
mysql> desc user;
+------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(60) | YES | | NULL | |
| password | char(32) | YES | | NULL | |
| birthday | date | YES | | NULL | |
| image_path | varchar(128) | YES | | NULL | |
+------------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
4>修改表的Field属性
-- 当前表的属性
mysql> desc user;
+------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(60) | YES | | NULL | |
| birthday | date | YES | | NULL | |
| image_path | varchar(128) | YES | | NULL | |
+------------+--------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
-- 修改某一属性，如name改为xingming
mysql> alter table user change name xingming varchar(60) DEFAULT NULL;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
-- 查看修改后的表的属性
mysql> desc user;
+------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| xingming | varchar(60) | YES | | NULL | |
| birthday | date | YES | | NULL | |
| image_path | varchar(128) | YES | | NULL | |
+------------+--------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
5>删除表中某一列
-- 查看当前表的属性
mysql> desc user;
+------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(60) | YES | | NULL | |
| password | char(32) | YES | | NULL | |
| birthday | date | YES | | NULL | |
| image_path | varchar(128) | YES | | NULL | |
+------------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
-- 查看当前表的内容
mysql> select * from user;
+------+--------+----------+------------+------------+
| id | name | password | birthday | image_path |
+------+--------+----------+------------+------------+
| 1 | 张三 | 12345 | 2010-10-01 | NULL |
| 1 | 李四 | 23456 | 2015-01-01 | NULL |
+------+--------+----------+------------+------------+
2 rows in set (0.00 sec)
-- 修改表，删除其中的password列
mysql> alter table user drop password;
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
-- 查看修改后的表的属性
mysql> desc user;
+------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(60) | YES | | NULL | |
| birthday | date | YES | | NULL | |
| image_path | varchar(128) | YES | | NULL | |
+------------+--------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
-- 查看修改后的表的内容
mysql> select * from user;
+------+--------+------------+------------+
| id | name | birthday | image_path |
+------+--------+------------+------------+
| 1 | 张三 | 2010-10-01 | NULL |
| 1 | 李四 | 2015-01-01 | NULL |
+------+--------+------------+------------+
2 rows in set (0.00 sec)
④删除表
-- 显示所有的表
mysql> show tables;
+-------------------+
| Tables_in_user_db |
+-------------------+
| user |
+-------------------+
1 row in set (0.00 sec)
-- 删除表
mysql> drop table user;
Query OK, 0 rows affected (0.00 sec)
-- 显示更改后所有的表
mysql> show tables;
Empty set (0.00 sec)
