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‎.idea/.gitignore‎

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‎.idea/MySQL.iml‎

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‎1.基本知识/1.数据类型和约束.sql‎

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# 数据类型 详见：https://blog.csdn.net/anxpp/article/details/51284106
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# 使用原则：够用就行,节省空间
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# 常用数据类型：
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# 整型：int bit
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# 小数：decimal decimal(5,2)表示共存5位数,小数位占2位
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# 字符串：varchar char varchar表示可变长字符串 char表示不变字符串例如char(3) 如果为'ab'则为‘ab ’
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# 字符串text：表示存储大字符串，当字符串大于4000时推荐使用
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# 日期类型：data time datatime
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# 枚举类型：enum
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# 对于图像、视频、音频文件一般存储于服务器上,然后在表中存储文件的路径
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# 约束
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# 主键：primary key :物理上存储的顺序
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# 非空：not null
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# 唯一：unique:此字段的值不能重复
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# 默认：default
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# 外键：foreign key 外健是指存储一个表主键值的字段 能起到一定的约束作用 但是不是外键越多越好 会降低查询效率

‎1.基本知识/2.数据库的操作.sql‎

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# 登陆数据库
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# mysql -uroot -p我的密码;
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# 退出数据库
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# exit/quit/ctrl+d
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# 显示时间
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select now();
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# 显示版本
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select version();
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# 创建数据库
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create database python_test char set = utf8;
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# 查看创建数据库的语句
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show create database python_test;
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# 删除数据库
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drop database python_test;
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# 使用数据库
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use python_test;
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# 查看当前使用数据库
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select database();
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