MongoDB Fundamentals: Document Model, BSON, and CentOS 7 Installation

Introduction to NoSQL and MongoDB

NoSQL (Not Only SQL) refers to non-relational databases that have grown beyond traditional SQL capabilities. Unlike relational databases, NoSQL stores data in non-tabular forms and offers advantages such as flexible data models, horizontal scalability for large-scale storage, fast retrieval without JOINs, and developer-friendly interfaces.

NoSQL Database Types

NoSQL databases are primarily categorized into four types:

Document databases

Key-value databases

Wide-column databases

Graph databases

MongoDB Overview

MongoDB is an open-source, distributed document database that provides document-oriented storage. It is considered the NoSQL database most similar to relational databases, offering a gentle learning curve for traditional database users. Key advantages include flexible schema, horizontal scaling, high performance, and rich query capabilities.

Core Concepts: Fields, Documents, Collections, Databases

MongoDB's storage structure consists of:

Field : A key-value pair (name-value), similar to a column in relational databases. A document contains zero or more fields.

Document : The basic data unit, a record in a collection, stored in BSON (Binary JSON) format which extends JSON with additional data types.

Collection : A group of documents, analogous to a table. Documents within a collection can have different fields.

Database : A container for multiple collections, similar to a relational database. A MongoDB server typically hosts multiple databases, each with its own files on the filesystem.

Comparison with Relational Database Concepts

The following diagram illustrates the mapping between MongoDB and relational database terminology:

BSON Document Structure

MongoDB records are BSON documents composed of key-value pairs. Field keys are strings; values can include nested documents, arrays, and other BSON types. The example below shows a sample document from the official documentation:

Installing MongoDB 7.0 on CentOS 7

Method 1: YUM Repository Installation

Create a repository file: vi /etc/yum.repos.d/mongodb-org-7.0.repo Add the following configuration:

[Mongodb-org-7.0]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/7.0/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-7.0.asc

Then install:

sudo yum install -y mongodb-org

Method 2: Manual RPM Installation

Download the required RPM packages from the official MongoDB download center (select version 7.0, platform Red Hat/CentOS 7, package type RPM). The download page appears as follows:

Also download the MongoDB Shell (mongosh) package:

Upload the RPM files to a directory (e.g., /opt/mongodb) and install with:

rpm -ivh mongodb-org-server-7.0.2-1.el7.x86_64.rpm
rpm -ivh mongodb-org-mongos-7.0.2-1.el7.x86_64.rpm
rpm -ivh mongodb-mongosh-2.0.2.x86_64.rpm

Verification

Run the MongoDB shell and list databases to confirm successful installation:

mongosh
show dbs

If the command executes and displays existing databases, the installation is successful.