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在终端或者DOS命令输入 连接mysql数据库
mysql -uroot -h[默认本机127.0.0.1/localhost] -P[3306] -p密码
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查看mysql版本信息和用户名
select version(),user();
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查看所有数据库:show databases ;
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查看所有数据表:show tables;
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SQL的组成
(1).DML主要用来插入修改和删除数据库中的数据,如insert、update、delete等
(2).DDL用来建立数据库、数据库对象和定义其列,大部分以create开头的命令,如create table、create view、drop table等
(3).DQL用来对数据库中数据进行查询,如select等
(4).DCL用来控制数据库组件的存取许可、存储权限等如grant、gevoke等
除此外,SQL还包括变量说明、内部函数等其他命令
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SQL中的运算符
1. 算数运算符:+(加)、-(减)、*(乘)、/(除)、%(模,即取余)。
2. 赋值运算符:=
3. 比较运算符:=、<、>、<>不等于、>=、<=、!=(不等于非SQL-92标准)
4. 逻辑运算符:and(&&)、or(||)、not(!)
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MySQL中数据库基本操作
数据库类型分为系统数据库和用户数据库。
创建数据库:create database [if not exists] 数据库名;
删除数据库:drop database [if exists] 数据库名;
查看数据库列表:show databases;
选择数据库:use 数据库名;