Koa2 Node学习

安装底座：

1.npm i koa-generator 2.koa2 -e koa2-weibo-code 3.nom run dev

安装插件： 1.npm i cross-env -D

安装 koa2-cors 解决跨域

npm i koa2-cors -S

// 处理跨域 
const cors = require('koa2-cors');

// 配置中间件
app.use(cors({
  origin:function(ctx){
    return 'http://localhost:8080';
  }
}))

MysSql写法：

1.基础用法
use koa2_weibo_db;

-- select * from blogs;
select count(id) as `count` from blogs; -- 计算总数
select * from blogs order by id desc limit 2 offset 1; -- 计算分页

表的关联

select * from blogs order by id desc;
insert into blogs (title,content,userid) values ('标签','内容3453',2) --关联插入对应位置
delete from users where id =1 --关联删除对应位置

-- select * from blogs order by id desc; -- 查询倒序
-- insert into blogs (title,content,userid) values ('标签3','内容3',3)
-- update  blogs  set content='内容345' where id='2'; -- 更新数据
--  delete from blogs where id=5; -- 删除数据

连表查询

select * from blogs inner join users on users.id=blogs.userid

//以下比较清晰 没有重复id
select blogs.* ,users.username,users.nickname from  blogs inner join users on users.id=blogs.userid;

//带上查询条件
select blogs.* ,users.username,users.nickname from  blogs inner join users on users.id=blogs.userid where users.username='zhangsan1';

Redis