---
title: "Document-oriented database"
chunk: 2/2
source: "https://en.wikipedia.org/wiki/Document-oriented_database"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T09:54:05.454091+00:00"
instance: "kb-cron"
---

=== Relationship to relational databases ===
In a relational database, data is organized into predefined types represented as tables. Each table contains rows (records) with a fixed set of columns (fields), so all records in a table share the same structure. Administrators typically define indexes on selected fields to improve query performance. A central principle of relational database design is database normalization, in which data that might otherwise be repeated is stored in separate tables and linked using keys. When records in different tables are related, a foreign key is used to associate them. 
For example, an address book application may store a contact's name, image, phone numbers, mailing addresses, and email addresses. In a normalized relational design, separate tables might be created for contacts, phone numbers, and email addresses. The phone number table would include a foreign key referencing the associated contact. To reconstruct a complete contact record, the database retrieves related information from each table using the foreign keys and combines it into a single record.
In contrast, a document-oriented database stores all data related to an object within a single document, and stored in the database as a single entry. In the address book example,the contact's name, image, and contact information may be stored together in one document. The document is retrieved using a unique key, and all related information is returned together, without needing to look up multiple tables.
A key difference between the document-oriented and relational models is that the data formats are not predefined in the document case. In most cases, any sort of document can be stored in a database, and documents can change in type and form over time. For example, a new field such as COUNTRY_FLAG can be added to new documents as they are inserted without affecting existing documents. To aid retrieval, document-oriented systems generally allow the administrator to provide hints to the database for locating certain types of information. These hints work in a similar fashion to indexes in relational databases. Many systems also allow additional metadata outside the content of the document itself, such as tagging entries as part of an address book, which enables retrieval of related information, for instance, all the address book entries. This provides functionality similar to a table, but separates the concept (categories of data) from its physical implementation (tables).
In the traditional normalized relational model, objects in the database are represented as separate rows of data, with no inherent structure beyond what is defined in the tables. This can create difficulties when translating programming objects to and from their corresponding database rows, a challenge known as object-relational impedance mismatch. In contrast, document stores often map programming objects directly into the database, preserving much of their internal structure. Databases using this approach are frequently described as NoSQL systems.

== Implementations ==

=== XML database implementations ===

Most XML databases are document-oriented databases.

== See also ==
Database theory
Data hierarchy
Data analysis
Full-text search
In-memory database
Internet Message Access Protocol (IMAP)
Machine-readable document
Multi-model database
NoSQL
Object database
Online database
Real-time database
Relational database
Content management system

== Notes ==

== References ==

== Further reading ==
Arkin, Assaf. (September 20, 2007). "Read Consistency: Dumb Databases, Smart Services."Labnotes: Don't Let the Bubble Go to Your Head! Archived March, 27 2008 at the Wayback Machine.

== External links ==
DB-Engines Ranking of Document Stores by popularity, updated monthly