Orientdb 简明教程
OrientDB - Overview
OrientDB 是一个开源 NoSQL 数据库管理系统。 NoSQL Database 提供了一种存储和检索无关系或非关系数据（指除表格数据之外的数据，比如文档数据或图表数据）的机制。NoSQL 数据库越来越多地在大数据和实时网络应用程序中使用。NoSQL 系统有时也称为“不只是 SQL”，以强调它们可能支持类似 SQL 的查询语言。
OrientDB is an Open Source NoSQL Database Management System. NoSQL Database provides a mechanism for storing and retrieving NO-relation or NON-relational data that refers to data other than tabular data such as document data or graph data. NoSQL databases are increasingly used in Big Data and real-time web applications. NoSQL systems are also sometimes called "Not Only SQL" to emphasize that they may support SQL-like query languages.
OrientDB 也属于 NoSQL 系列。OrientDB 是一个第二代分布式图表数据库，具有一款产品的文档灵活性，并采用 Apache 2 的开源许可。在 OrientDB 之前，市场上已有几个 NoSQL 数据库，其中之一是 MongoDB。
OrientDB also belongs to the NoSQL family. OrientDB is a second generation Distributed Graph Database with the flexibility of Documents in one product with an open source of Apache 2 license. There were several NoSQL databases in the market before OrientDB, one of them being MongoDB.
MongoDB vs OrientDB
MongoDB 和 OrientDB 包含许多常见功能，但引擎从根本上是不同的。MongoDB 是纯文档数据库，而 OrientDB 是混合文档图表引擎。
MongoDB and OrientDB contains many common features but the engines are fundamentally different. MongoDB is pure Document database and OrientDB is a hybrid Document with graph engine.
Features |
MongoDB |
OrientDB |
Relationships |
Uses the RDBMS JOINS to create relationship between entities. It has high runtime cost and does not scale when database scale increases. |
Embeds and connects documents like relational database. It uses direct, super-fast links taken from graph database world. |
Fetch Plan |
Costly JOIN operations. |
Easily returns complete graph with interconnected documents. |
Transactions |
Doesn’t support ACID transactions, but it supports atomic operations. |
Supports ACID transactions as well as atomic operations. |
Query language |
Has its own language based on JSON. |
Query language is built on SQL. |
Indexes |
Uses the B-Tree algorithm for all indexes. |
Supports three different indexing algorithms so that the user can achieve best performance. |
Storage engine |
Uses memory mapping technique. |
Uses the storage engine name LOCAL and PLOCAL. |
OrientDB是第一个多模型开源NoSQL DBMS，它将图的功能和文档的灵活性集合在一个可伸缩的高性能操作数据库中。
OrientDB is the first Multi-Model open source NoSQL DBMS that brings together the power of graphs and flexibility of documents into a scalable high-performance operational database.