題目：雲服務器上多種類型數據庫的性能比較和原理探究
我們選取了三種不同類型的數據庫：Mysql、MongoDB、Redis 來測試它們在不同種類的雲服務器上的讀寫性能、網絡併發性能、存儲性能、CPU佔用率、事務處理能力以及安全性能方面的區別，並且結合數據庫的底層實現原理來解釋這種性能方面的區別。
其中
Mysql是一種關係型數據庫。
關係型數據庫是一種基於關係的數據庫，而關係模型可通過二維表來進行表示，所以數據的存儲方式是由行列組成的表，每一列是一個字段，每一行是一個記錄。在關係型數據庫中通常包含了三個概念：數據庫（database）、表（table）、記錄（record）。Mysql常用B+樹進行索引。
Redis和MongoDB是非關係型數據庫。
MongoDB是由c++語言編寫的非關係型數據庫，是一個基於分佈式文件存儲的開源數據庫系統，其內容存儲類似JSON對象，它的字段可以包含其他的文檔、數組以及文檔數組。MongoDB包含了三個層次概念：數據庫（database）、集合（collection）、文檔（document）。MongoDB的數據索引是B-樹。
Redis是一種內存數據庫，所有的數據都是放在內存之中，定期寫入磁盤中，當內存不夠的時候，可選擇指定的LRU算法刪除數據。Redis是基於哈希字典建立的，因此其索引方式是哈希。
在探究不同數據庫性能上的區別的同時，我們也會結合各種數據庫在不同種類雲服務器上運行性能的區別，進行綜合的分析。
Title: Performance Comparison and Principle Exploration of Various Types of Databases on Cloud Servers
We selected three different types of databases: Mysql, MongoDB, and Redis to test their differences in read and write performance on different types of cloud servers, network concurrency performance, storage performance, CPU usage, transaction processing capabilities, and security performance. And combined with the underlying implementation of the database to explain this performance difference.
Mysql is a relational database.
A relational database is a relational database, and a relational model can be represented by a two-dimensional table. Therefore, the data is stored in a table consisting of rows and columns. Each column is a field and each row is a record. Relational databases usually contain three concepts: database, table, and record. Mysql often uses B + trees for indexing.
Redis and MongoDB are non-relational databases.
MongoDB is a non-relational database written in the C ++ language. It is an open source database system based on distributed file storage. Its content store is similar to JSON objects, and its fields can contain other documents, arrays, and document arrays. MongoDB includes three levels of concepts: database, collection, and document. MongoDB's data index is a B-tree.
Redis is a kind of memory database. All data is stored in memory and written to disk periodically. When the memory is not enough, you can choose the specified LRU algorithm to delete the data. Redis is based on a hash dictionary, so its indexing method is hash.
While exploring the differences in the performance of different databases, we will also conduct a comprehensive analysis of the differences in the performance of various databases on different types of cloud servers.
相關參考：
數據庫性能指標評估模型
