1. 沙发数据库：
Apache CouchDB 是一个开源的面向文档的 NoSQL 数据库，它使用多种格式和协议来存储、传输和处理其数据，它使用 JSON 存储数据，使用 MapReduce 作为其查询语言的 JavaScript，以及用于 API 的 HTTP。它由 Apache 软件基金会开发，最初于 2005 年发布。它是用 Erlang 编写的。
2. PostgreSQL :
PostgreSQL 是一个强大的开源对象关系数据库系统。由于其高稳定性，它以低维护工作提供良好的性能。 PostgreSQL 是第一个实现多版本并发控制 (MVCC) 功能的 DBMS。
CouchDB 和 PostgreSQL 的区别：
| S.NO. | COUCHDB | POSTGRESQL |
|---|---|---|
| 1. | Developed by Apache Software Foundation and initially released in 2005. | Developed By PostgreSQL Global Development Group on 1989. |
| 2. | It is native JSON – document store inspired by Lotus Notes, scalable from globally distributed server-clusters down to mobile phones. | It is widely used open source RDBMS. |
| 3. | CouchDB is written in Erlang. | PostgreSQL is written in C languages. |
| 4. | The primary database model for CouchDB is Document Store. | The primary database model for PostgreSQL is Relational DBMS. |
| 5. | It does not supports SQL query language. | It supports SQL query language. |
| 6. | Server operating systems for CouchDB are Android, BSD, Linux, OS X, Solaris and Windows. | Server operating systems for PostgreSQL are FreeBSD, HP-UX, Linux, NetBSD, OpenBSD, OS X, Solaris, Unix and Windows. |
| 7. | It does not supports predefined data types. | It supports predefined data types such as string, integer, float or date. |
| 8. | It does not support XML Format. | It supports XML Format. |
| 9. | It support two replication methods – Master-master replication and Master-slave replication. | It support only one replication methods – Master-master replication. |
| 10. | In CouchDB, partitioning can be done by Sharding. | In PostgreSQL, partitioning can be done by range, list and hash. |