197 lines
2.6 KiB
Markdown
197 lines
2.6 KiB
Markdown
# 原创
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： 第一章 数据库和SQL
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# 第一章 数据库和SQL
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>
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参考书籍：[https://book.douban.com/subject/27055712/](https://book.douban.com/subject/27055712/)
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#### 目录
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### 1、法则
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### 2、SQL书写规则
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### 3、权限管理
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MySQL 的账户信息保存在 mysql 这个数据库中。
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```
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USE mysql;
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SELECT user FROM user;
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```
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**创建账户**
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新创建的账户没有任何权限。
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```
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CREATE USER myuser IDENTIFIED BY 'mypassword';
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```
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**修改账户名**
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```
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RENAME myuser TO newuser;
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```
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**删除账户**
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```
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DROP USER myuser;
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```
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**查看权限**
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```
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SHOW GRANTS FOR myuser;
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```
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**授予权限**
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账户用 username@host 的形式定义，username@% 使用的是默认主机名。
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```
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GRANT SELECT, INSERT ON mydatabase.* TO myuser;
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```
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**删除权限**
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GRANT 和 REVOKE 可在几个层次上控制访问权限：
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```
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REVOKE SELECT, INSERT ON mydatabase.* FROM myuser;
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```
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**更改密码**
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必须使用 Password() 函数
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```
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SET PASSWROD FOR myuser = Password('new_password');
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```
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### 4、SQL常用命令
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修改MySQL提示符:
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```
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mysql -uroot -proot --prompt 提示符 # 连接客户端时通过参数指定
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prompt 提示符 # 连接客户端之后，通过prompt指定
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```
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<th align="center">参数</th><th align="center">描述</th>
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|------
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<td align="center">\D</td><td align="center">完整的日期</td>
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<td align="center">\d</td><td align="center">当前数据库</td>
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<td align="center">\h</td><td align="center">服务器名称</td>
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<td align="center">\u</td><td align="center">当前用户</td>
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```
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CREATE {DATEBASE | SCHEMA} [IF NOT EXISTS] db_name [DEFAULT] CHARACTER SET [=] charset_name
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```
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```
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SHOW {DATABASE | SCHEMAS} [LIKE "pattern" | WHERE expr]
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```
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```
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SHOW WARNINGS;
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```
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```
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SHOW CREATE DATABASE t1;
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```
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```
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ALTER {DATABASE | SCHEMA} [db_name] [DEFAULT] CHARACTER SET [=] charset_name
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```
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```
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DROP {DATABASE |SCHEMA} [IF EXISTS] db_name;
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```
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```
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SELECT *
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FROM mytable; -- 注释
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/* 注释1
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注释2 */
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```
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### 5、表的创建、修改和插入
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#### 创建表
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```
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CREATE TABLE mytable (
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id INT NOT NULL AUTO_INCREMENT,
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col1 INT NOT NULL DEFAULT 1,
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col2 VARCHAR(45) NULL,
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col3 DATE NULL,+
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PRIMARY KEY (`id`)); --设定主键
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```
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#### 修改表
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添加列
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```
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ALTER TABLE mytable
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ADD col CHAR(20);
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```
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删除列
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```
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ALTER TABLE mytable
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DROP COLUMN col;
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```
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**删除表**
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```
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DROP TABLE mytable;
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```
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修改表名
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```
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ALTER TABLE <原表名> to <新表名>
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```
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#### 插入表数据
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普通插入，不指定列则要求全部要插入
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```
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START TRANSACTION;
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INSERT INTO mytable(col1, col2)
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VALUES(val1, val2);
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...
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COMMIT;
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```
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