Introduction to MongoDB

MongoDB® is an open-source NoSQL database. MongoDB stores data in JSON-like documents that can vary in structure. Because MongoDB uses dynamic schemas, users can create records without defining the data structure first.

MongoDB stores related information together, which enables queries to process more quickly. To retrieve information, users leverage the MongoDB query language.


For an introduction to NoSQL databases, see the following articles:

Terminology and concepts

Many concepts in MongoDB have close analogies to concepts in relational databases such as Oracle Database®. The following table compares the basic terminology and concepts:

MongoDBOracle Database
Embedded documents and linkingJoins

Feature comparison

The following table compares the features of MongoDB with the features of Oracle Database:

FeatureMongoDBOracle Database
Rich data modelYesNo
Dynamic schemaYesNo
Typed dataYesYes
Data localityYesNo
Field updatesYesYes
Easy for programmersYesNo

Query language

Both MongoDB and Oracle Database have their own rich query language. However, there are some differences between them. Oracle Database supports procedures and functions for manipulating the data returned from the SELECT statement to handle advanced queries. In contrast, MongoDB uses callback functions for advanced queries. The mongo shell uses the JavaScript programming language to run these functions.

Can you use MongoDB and Oracle Database together?

Yes. There are many examples of hybrid deployments of MongoDB and Oracle Database, particularly among e-commerce applications. The flexible data model that MongoDB uses is a good fit for product catalogs because catalogs typically include multiple products with different attributes. However, Oracle Database is generally used for checkout systems because these systems require complex transactions.

Oracle Database is better suited to handle such transactions because it uses ACID (Atomicity, Consistency, Isolation, Durability) as its integrity model. This model gives Oracle Database integrity features that MongoDB doesn't offer, such as isolation, referential integrity, and revision control.

In other cases, new business requirements push organizations to adopt MongoDB to incorporate next-generation components into their applications. For example, both MongoDB and Oracle Database use conditional entry updates, composite keys, Unicode characters, and full-text search. However, MongoDB also has a built-in map-reduce function for aggregating large amounts of data.

Next step

Introduction to Apache Cassandra®

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