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YiRanCN committed Aug 15, 2023
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8 changes: 0 additions & 8 deletions docs/me/index.md
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[YiRanCN](https://github.com/YiRanCN),这是我的 GitHub 主页,欢迎大家 follow 和 star。

### 我致力于:从无到有,一行一行,码出一个免费、开源的物联网云平台,加油!

[![微信](https://img.shields.io/badge/%E5%BE%AE%E4%BF%A1-yiranchengnan-blue)](https://img.shields.io/badge/%E5%BE%AE%E4%BF%A1-yiranchengnan-blue)
[![mail](https://img.shields.io/badge/mail-cniiot%40163.com-brightgreen)](mailto:cniiot@163.com)

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- 其他

[物联网云平台产品架构](https://github.com/YiRanCN/YiRanCN/blob/main/%E7%89%A9%E8%81%94%E7%BD%91%E4%BA%91%E5%B9%B3%E5%8F%B0%E4%BA%A7%E5%93%81%E6%9E%B6%E6%9E%84.md)

[物联网云平台-后端源码](https://github.com/YiRanCN/iot-cloud-backend)

[物联网云平台-前端源码](https://github.com/YiRanCN/iot-cloud-frontend)

[物联网云平台-APP 端源码](https://github.com/YiRanCN/iot_cloud_flutter)
8 changes: 8 additions & 0 deletions docs/study/back/index.md
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# 概述

后端是相当于前端来说的,用户看不到的内容统一成为后端,后端包括但不限于:

- API 接口
- 数据库
- 协议交互服务端
- websocket 服务端
- 短信、邮件服务
- 集群服务、分布式服务
5 changes: 5 additions & 0 deletions docs/study/competitive/ThingsCloud.md
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# ThingsCloud

参考,参考,绝对可以参考。

[官方网站](https://www.thingscloud.xyz/)
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# 概述

物联网行业的一些业务分析、公司分析、行业分析。
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# MySQL 笔记

### WITH 查询

MySQL 语句 WITH 是 MySQL 8.0 中的一个新特性,用于帮助简化复杂查询以及提高查询效率。在大多数情况下,查询都需要多次嵌套使用,这导致查询语句写得很长且难以维护。WITH 语句就是用来解决这个问题的,它是一种临时表的方式,得到的结果集可以作为查询的结果集。在 WITH 语句中,可以定义多个别名,然后嵌套使用。

```sql
WITH t1 AS (
SELECT col1 FROM table1
),
t2 as (
SELECT col1 FROM table2
)
--使用
SELECT * FROM t1 INNER JOIN t2 ON t1.col1 = t2.col1;
```

在这个例子中,我们定义了两张表,t1 和 t2,然后使用了这两张表来进行查询,这样我们就可以避免在查询语句中多次嵌套使用相同的子查询,并且也不需要为每个查询定义一个临时表。

with 特性:

- with 其实就是一个子查询抽取出来,换了一个别名
- 和视图的区别:with as 等同于一次性视图,只会持续到下一个查询。在之后就不能再被引用
- 主要用于简化复杂的 数据集 和 递归

其实 WITH 表达式除了和 SELECT 一起用, 还可以有下面的组合:

insert with 、with update、with delete、with with、with recursive(可以模拟数字、日期等序列)、WITH 可以定义多张表

```sql
with_clause:
WITH [RECURSIVE]
cte_name [(col_name [, col_name] ...)] AS (subquery)
[, cte_name [(col_name [, col_name] ...)] AS (subquery)] ...
```

### 递归共用表达式 with recursive

```sql
WITH RECURSIVE cte (n) AS
(
SELECT 1
UNION ALL
SELECT n + 1 FROM cte WHERE n < 5
)
SELECT * FROM cte;
```

### 参考文档

- [MySQL 8.0 with 语法(cte)](https://halo.sherlocky.com/archives/mysql-8-cte)
- [MySQL 8.0 官方文档](https://dev.mysql.com/doc/refman/8.0/en/preface.html)
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# 概述

存储数据的服务统一成为数据库,包括但不限于:

- 关系数据库 msyql、oracle 等
- 非关系数据库 redis、MongoDB 等
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# 概述

一种虚拟技术。
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# 概述

所有用户看到的界面,统一成为前端,包括但不限于:

- PC WEB
- 移动端 WEB
- 小程序
- 桌面程序
1 change: 1 addition & 0 deletions docs/study/program/index.md
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# 概述

写代码用到的一套规范及其延伸工具。
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# 概述

跨越编程语言的一些套路。
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# 概述

主要使用 Java,中间件可集成或独立部署。

- MQTT Broker 采用 hivemq 集成
- redis
- mysql
- kafka
- influxdb
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# 概述

一般需要包括如下内容:

- Jenkins 持续集成、部署
- Grafana+哨兵 监控服务
- 各种运维脚本

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