MongoDB面试题集锦
什么是NoSQL数据库？NoSQL和RDBMS有什么区别？在哪些情况下使用和不使用NoSQL数据库？
1.什么是NoSQL数据库？NoSQL和RDBMS有什么区别？在哪些情况下使用和不使用NoSQL数据库？
NoSQL是非关系型数据库，NoSQL = Not Only SQL。
关系型数据库采用的结构化的数据，NoSQL采用的是键值对的方式存储数据。
在处理非结构化/半结构化的大数据时；在水平方向上进行扩展时；随时应对动态增加的数据项时可以优先考虑使用NoSQL数据库。
在考虑数据库的成熟度；支持；分析和商业智能；管理及专业性等问题时，应优先考虑关系型数据库。
2.非关系型数据库有哪些？
Membase、MongoDB、Hypertable
3.MySQL和MongoDB之间最基本的区别是什么？
关系型数据库与非关系型数据库的区别，即数据存储结构的不同。
4.MongoDB的特点是什么？
（1）面向文档（2）高性能（3）高可用（4）易扩展（5）丰富的查询语言
5. MongoDB支持存储过程吗？如果支持的话，怎么用？
MongoDB支持存储过程，它是javascript写的，保存在db.system.js表中。
6.如何理解MongoDB中的GridFS机制，MongoDB为何使用GridFS来存储文件？
GridFS是一种将大型文件存储在MongoDB中的文件规范。使用GridFS可以将大文件分隔成多个小文档存放，这样我们能够有效的保存大文档，而且解决了BSON对象有限制的问题。
7.为什么MongoDB的数据文件很大？
MongoDB采用的预分配空间的方式来防止文件碎片。
8.当更新一个正在被迁移的块（Chunk）上的文档时会发生什么？
更新操作会立即发生在旧的块（Chunk）上，然后更改才会在所有权转移前复制到新的分片上。
9.MongoDB在A:{B,C}上建立索引，查询A:{B,C}和A:{C,B}都会使用索引吗？
不会，只会在A:{B,C}上使用索引。
10.如果一个分片（Shard）停止或很慢的时候，发起一个查询会怎样？
如果一个分片停止了，除非查询设置了“Partial”选项，否则查询会返回一个错误。如果一个分片响应很慢，MongoDB会等待它的响应。
MongoDB 的详细介绍：请点这里
MongoDB 的下载地址：请点这里
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