一、数据库介绍

数据库 - 数据的仓库 - database
关系型数据库 - 数据持久化 - 管理数据 - 方便的检索数据
理论基础：集合论、关系代数
表象：用二维表存储数据

• 行 - row - 记录
• 列 - column - 字段 - 数据类型
• 主键列 - primary key - 唯一标识一条记录
  有自己的编程语言：结构化查询语言 - SQL

DB - database
DBMS - database management system
DBA - database administrator
DBS - database system = DB + DBMS + DBA

关系型数据库的产品（数据库管理系统）：

1. Oracle
2. MySQL ---> 服务器+客户端工具
   C/S应用模式 - Client / Server

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IBM - DB2
微软 - SQL Server
PostgreSQL

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Redis - 键值对数据库
MongoDB - 文档数据库
ElasticSearch/Solr - 搜索引擎

Windows系统

启动MySQL服务器

1. Win+R ---> 运行
2. services.msc ---> 服务
3. MySQL57 ---> 启动

net start mysql57

通过客户端程序连接服务器
开始菜单 ---> MySQL ---> MySQL Client Program
图形化的客户端程序
Navicat for MySQL - 猫
SQLyog - 海豚
Toad for MySQL - 蟾蜍

二、简单的mysql

-- 关系型数据库
-- 关系代数 + 集合论
-- 用二维表组织数据（行和列）
-- 结构化查询语言（SQL）
-- SQL: Structured Query Language - 结构化查询语言 - 不区分大小写
-- 1. DDL: Data Definition Language - 数据定义语言 - create / drop / alter
-- 2. DML: Data Manipulation Language - 数据操作语言 - insert / delete /
update / select
-- 3. DCL: Data Control Language - 数据控制语言 - grant / revoke /
commit / rollback
-- 如果存在名为school的数据库就删除
drop database if exists school;
-- 创建school数据库并设置默认字符集为utf8
create database school default charset utf8;
-- 切换到school数据库的上下文环境
use school;
-- 如果存在名为tb_student的表就删除
drop table if exists tb_student;
-- 查看MySQL支持哪些数据类型
-- ? data types
-- ? int
-- ? varchar
-- 创建学生表tb_student
create table tb_student
(
stuid int not null comment '学号',
stuname varchar(31) not null comment '姓名',
stusex enum('男', '女') default '男' comment '性别',
stubirth date comment '出生日期',
stuaddr varchar(255) comment '家庭住址',
primary key (stuid)
);
-- 修改tb_student表的表结构添加一个新列
alter table tb_student add column stutel char(11) comment '联系电话';
-- 修改tb_student表的表结构删除一个列
alter table tb_student drop column stutel;
-- 修改tb_student表的表结构修改一个列
alter table tb_student change column stuname stuname varchar(20)
not null comment '姓名';
-- 如果存在名为tb_course的表就删除
drop table if exists tb_course;
-- 创建课程表tb_course
create table tb_course
(
cid int not null comment '课程编号',
cname varchar(31) not null comment '课程名称',
credit tinyint unsigned not null comment '学分',
cdate timestamp default now() comment '开课日期',
primary key (cid)
);
-- 录入完整的学生数据
insert into tb_student values
(1001, '骆昊', '男', '1980-11-28', '四川成都');
-- 指定列录入对应的数据
insert into tb_student (stuid, stuname, stubirth)
values (1002, '王大锤', '1990-2-2');
-- 一次性插入多条数据
insert into tb_student
(stuid, stuname, stusex)
values
(1003, '白元芳', default),
(1004, '白洁', '女'),
(1005, '狄仁杰', '男'),
(1006, '武则天', '女');
-- 录入课程数据
insert into tb_course
(cid, cname, credit)
values
(1111, 'Python程序设计', 3),
(2222, 'Web前端开发', 2),
(3333, 'Linux系统入门', 2),
(4444, '数据库理论和实践', 3),
(5555, '企业应用架构', 2);
-- 删除记录
delete from tb_student where stuid=3001;
delete from tb_student where stuid>1005;
delete from tb_student where stuid between 1003 and 1005;
-- 删全表
truncate table tb_student;
-- 更新记录
update tb_student set stubirth='1995-5-5' where stuname='白元芳';
update tb_student set stubirth='1996-6-6', stuaddr='河北保定'
where stuid=1004;
update tb_course set credit=4 where cid in (2222, 5555);
update tb_course set credit=2 where cid=2222 or cid=5555;
-- 查询记录
select * from tb_student;
select * from tb_course;
-- 投影
select stuid, stuname, stusex from tb_student;
-- 别名
select stuid as 学号, stuname as 姓名, stusex as 性别 from tb_student;
-- 筛选
select stuid, stuname, stusex from tb_student where stusex='男';
select stuname, stubirth from tb_student
where stubirth between '1990-1-1' and '1999-12-31';
select stuname, stubirth, stusex from tb_student
where stubirth between '1990-1-1' and '1999-12-31' and stusex='男';
select stuname, stubirth, stusex from tb_student
where stubirth between '1990-1-1' and '1999-12-31' or stusex='男';
-- 集合运算in和not in
select stuid, stuname from tb_student
where stuid not in (1001, 1003, 1005, 2001);
-- 判断空值（null）不能用=或<>，需要使用is或is not
select * from tb_student where stuaddr is null;
select * from tb_student where stuaddr is not null;
insert into tb_student values (1007, '李白', default, null, null);
insert into tb_student values (1008, '李白菜', '女', null, null);
-- 模糊
select * from tb_student where stuname like '白%';
select * from tb_student where stuname like '%白';
select * from tb_student where stuname like '%白%';
select * from tb_student where stuname like '白';
select * from tb_student where stuname like '白';
select * from tb_student where stuname like '白';
select * from tb_student where stuname like '白';
select * from tb_student where stuname like '白';
-- 排序
select * from tb_student order by stuid desc;
select * from tb_student order by stuname asc;
select * from tb_student order by stusex desc, stuid desc;
-- 分页查询
select * from tb_student order by stuid desc limit 3;
select * from tb_student order by stuid desc limit 3 offset 3;
select * from tb_student order by stuid desc limit 3,3;
select * from tb_student order by stuid desc limit 3 offset 6;
select * from tb_student order by stuid desc limit 6,3;
select distinct substr(stuname, 1, 1) from tb_student;
select substr(stuname, 2, length(stuname)) from tb_student;
-- 聚合函数(统计函数)
select max(credit) from tb_course;
select min(credit) from tb_course;
select max(stubirth) from tb_student;
select min(stubirth) from tb_student;
select sum(credit) from tb_course;
select avg(credit) from tb_course;
select count(stuid) from tb_student;
select count(cid) from tb_course;
-- 分组查询
select stusex, count(stuid) from tb_student group by stusex;
-- 创建用户
create user 'wangdachui'@'%' identified by '1qaz2wsx';
create user 'wangdachui'@'localhost' identified by '1qaz2wsx';
-- 授权操作
grant all privileges on . to 'wangdachui'@'localhost';
grant all privileges on . to 'wangdachui'@'localhost' with grant option;
-- 召回权限
revoke all privileges on . from 'wangdachui'@'localhost';
grant select on school.* to 'wangdachui'@'localhost';
grant insert, delete, update on school.* to 'wangdachui'@'localhost';
grant create, drop, alter on school.* to 'wangdachui'@'localhost';
-- 表与表之间的关系
-- 一对一 （人和身份证、用户和购物车）
-- 一对多 / 多对一（人和银行卡、用户和订单）
-- 多对多（学生和课程、订单和商品）
-- 外键：外来的主键（其他表的主键）
-- 学生、课程、学院、老师