1. 微软 SQL 服务器：
Microsoft SQL Server 是一个关系数据库管理系统 (RDBMS)，它依赖于平台，并且是基于 GUI 和命令的软件。它支持企业 IT 环境中的各种事务处理、商业智能和分析应用程序。它由微软公司开发，最初于 1989 年 4 月 24 日发布。它是用 C 和 C++ 语言编写的。
2. 卡桑德拉：
Cassandra 是一个免费、开源、分布式、广泛的列存储、NoSQL 数据库管理系统。它由 Apache 软件基金会开发，最初于 2008 年 7 月发布。Cassandra 旨在处理跨多个商用服务器的大量数据，提供高可用性且无单点故障。
MS SQL Server 和 Cassandra 的区别：
| S.NO. | MS SQL Server | Cassandra |
|---|---|---|
| 1. | Developed by Microsoft Corporation and initially released on April 24, 1989. | Developed by Apache Software foundation and released on July 2008. |
| 2. | MS SQL server is written in C and C++. | Cassandra is written only in Java language. |
| 3. | The primary database model for MS SQL Server is Relational DBMS. | The primary database model for Cassandra is Wide Column Store. |
| 4. | MS SQL Server does supports the concept of secondary indexes without any restriction. | Secondary indexing in Cassandra is restricted. |
| 5. | The license for MS SQL Server is Commercial. | The license for Cassandra is Open Source. |
| 6. | MS SQL Server supports XML data format. | Cassandra does not supports XML data format. |
| 7. | In MS SQL Server the data schema is Fixed. | Cassandra is schema free. |
| 8. | MS SQL Server provides ACID transactions. | Cassandra does not provides ACID transactions. |
| 9. | MS SQL Server provides the concept of Referential Integrity and have Foreign keys. | There is no concept of Foreign keys in Casandra. |
| 10. | MS SQL Server does not supports Map Reduce method. | Cassandra supports Map Reduce method. |
| 11. | Server operating systems for MS SQL Server are Linux and Windows. | Server operating systems for Cassandra are BSD, Linux, OS X and Windows. |
| 12. | Famous companies like Citi, Bank of America, UPS, etc uses MS SQL Server. | Famous companies like Hulu, Instagram, Intuit, Netflix, Reddit, etc uses Cassandra. |