NoSQL 是為了解決RDBMS的3大問題：

1、可擴展性：比如跨不同機器對數(shù)據(jù)進行分區(qū)的能力。

2、提高性能：在某些情況下，RDBMS的性能比較低。

3、固定的Schema：RDBMS有很多好處（參照完整性，關(guān)系，觸發(fā)器等等），但是強迫你把所有數(shù)據(jù)存儲在一個固定的模式下（Schema）。

基本來說有幾種不同類型的NoSQL數(shù)據(jù)庫：

1、Key-Value：如Scalaris, Tokio Cabinet, Voldemort；

　　store data in key/value pairs: very efficient for performance and higly scalable, but difficult to query and to implement real world problems

2、Tabular：如Cassandra, Hbase, Hypertable, Google Bigtable；

　　store data in tabular structures, but columns may vary in time and each row may have only a subset of the columns

3、Document-Oriented：如CouchDb, MongoDb, Riak, Amazon SimpleDb；

　　like Key/Value but they let you nest more values for a key. This is a nice paradigm for programmers as it becomes easy, specially with script languages (Python, Ruby, PHP...), to implement a one to one mapping relation between the code objects and the objects (documents) in the database

4、Graph：如Neo4J, InfoGrid, AllegroGraph；

　　stores objects and relationships in nodes and edges of a graph. For situations that fit this model, like hierarchical data, this solution can be much much faster than the other ones.

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MongoDb is a document oriented NoSQL database. With such a database it is very easy to map the programming objects (documents) we want to store to the database. JSON is a very viable standard to do this mapping, and so MongoDb does: it stores JSON documents in the database.

To makes performance better JSON is stored by MongoDb in a efficient binary format called BSON. BSON is a binary serialization of JSON-like documents and stands for Binary JSON.

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http://www.rackspace.com/blog/nosql-ecosystem/

轉(zhuǎn)載于:https://www.cnblogs.com/winson/p/3270104.html

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