## 11.1 FAQ: MongoDB Fundamentals 

This document addresses basic high level questions about MongoDB and its use. 

## Frequently Asked Questions 

If you don’t find the answer you’re looking for, check the complete list of FAQs (page 743) or post your question to the MongoDB User Mailing List$^{1}$. 

## 11.1.1 What kind of database is MongoDB? 

MongoDB is a document -oriented DBMS. Think of MySQL but with JSON -like objects comprising the data model, rather than RDBMS tables. Significantly, MongoDB supports neither joins nor transactions. However, it features secondary indexes, an expressive query language, atomic writes on a per-document level, and fully-consistent reads. 

Operationally, MongoDB features master-slave replication with automated failover and built-in horizontal scaling via automated range-based partitioning. 

Note: MongoDB uses BSON , a binary object format similar to, but more expressive than JSON . 

## 11.1.2 Do MongoDB databases have tables? 

Instead of tables, a MongoDB database stores its data in collections , which are the rough equivalent of RDBMS tables. A collection holds one or more documents , which corresponds to a record or a row in a relational database table, and each document has one or more fields, which corresponds to a column in a relational database table. 

Collections have important differences from RDBMS tables. Documents in a single collection may have a unique combination and set of fields. Documents need not have identical fields. You can add a field to some documents in a collection without adding that field to all documents in the collection. 

## See 

SQL to MongoDB Mapping Chart (page 131) 

