Getting Started with MySQL (a)

Getting Started with MySQL (a)

What is a database

As the name suggests, it is a database management data warehouse (system).

Database Category:

1. Relations with non-relationship:

   Relations: a link between database tables and table - MySQL

   Non-relational: no concept of the table - Redis, MongoDB

2. Memory and hard drive:

   Hard Drive: permanent data storage - MySQL, MongoDB

   Memory: High --Redis data access efficiency, memcache

3. sql and nosql:

   sql: sql statement by the operation of the database

   nosql: database operation is in the form of Key-Value (value is a record)

MySQL open tour

First, connect MySQL different world!

Open cmd:

# 游客登录(mysql 8 已取消游客登录)
mysql

# 账号密码登录 mysql -u用户名 -p密码
mysql -uroot -p
# 输入回车后再次输入密码，密码不会显示

# 连接指定服务器的mysql ：mysql -h ip地址 -P 端口号 -u 账号 -p  
mysql -hlocalhost -P3306 -uroot -p

# 登入后退出
quit
exit

MySQL View landscape

# 查看当前用户
select user();

# root下查看所有用户信息
select * from mysql.user \G   # \G 可以竖行显示

# 修改密码
alter user user() identified by 'password'  # 修改当前用户密码
mysqladmin -uroot -p123 -hlocalhost password 123456  # 未登录状态下修改

# 创建用户并赋予权限
# 8.0之前：
grant 权限们 on 数据库名.表名 to 用户名@主机名 identified by '密码';
# 8.0后  无法一步完成了
create user 用户名@主机名 identified by '密码';
grant 权限们 on 数据库名.表名 to 用户名@主机名 with grant option;

The basic operation of the database (obtaining initial skills)

# 查看已有数据库
show databases;

# 选择数据库
use 数据库名；

# 查看当前所在数据库
select database();

# 创建数据库
create database 数据库名 [charset=编码格式];

# 查看创建数据库的详细内容
show create database 数据库名;

# 删库跑路
drop database 数据库名;

The basic operation of the table (initial skills)

# 查看已有的表
show tables;

# 建表 
create table 表名(字段名 数据类型(长度)，...) [engine=引擎]；

# 查看建表语句
show create table 表名;

# 查看表结构
desc 表名;

# 删表
drop table 表名;

Basic operation record (CRUD) (obtained basic skills)

# 查 
select 字段们 from [数据库名.]表名 where 条件;
select * from mysql.user;

# 增
insert [into] [数据库名.]表名[(字段名...)] values (值...);
insert into stu values ('du',18);
insert into stu values ('lu',18),('jin',26);  # 可同时赋值多条数据

# 改
update [数据库名.]表名 set 字段1=新值1, 字段n=新值n where 字段=旧值;

# 删
delete from [数据库名.]表名 where 条件;

# 清空表
truncate 表名;