Today, I want to share with you some of the basics stuff about MongoDB concept and commands, so If you are beginner to MongoDB, this article is recommended for you 😉
What is MongoDB !?
We can represent a MongoDB like a rich document-oriented NoSQL database that stores the data in the form of JSON documents with an autogenerated identified for every document.Â
NoSQL ?? yes !! A No-SQL database is a database where the table structure is not fixed, unlike the structure of the Tables on SQL databases.Â
So MongoDB stores the data in the form of JSON string irrespective of the count of attributes or names of attributes in a specific column.Â
This allows developers to quickly make changes to entities without needing to change anything in the database level. And this is the great power of the NOSQL databases.
Following are some of the key points in MongoDB vs RDBMS which clearly show differences between MongoDB and RDBMS (SQL Databases):
| RDBMS | MongoDB |
|---|---|
| Database | Database |
| Tables | Collections |
| Rows | Documents |
| Columns | Fields |
Comparing to a typical relational database, this is how MongoDB database looks like  :Â
MongoDB Server Versions :
| Release | Release Date | End of Life Date |
|---|---|---|
| MongoDB 4.4 | July 2020 | --- |
| MongoDB 4.2 | August 2019 | --- |
| MongoDB 4.0 | June 2018 | January 2022 |
| MongoDB 3.6 | November 2017 | April 2021 |
| MongoDB 3.4 | November 2016 | January 2020 |
| MongoDB 3.2 | December 2015 | September 2018 |
| MongoDB 3.0 | March 2015 | February 2018 |
| MongoDB 2.6 | April 2014 | October 2016 |
| MongoDB 2.4 | March 2013 | March 2016 |
| MongoDB 2.2 | August 2012 | February 2014 |
| MongoDB 2.0 | September 2011 | March 2013 |
| MongoDB 1.8 | March 2011 | September 2012 |
| MongoDB 1.6 | August 2010 | February 2012 |
| MongoDB 1.4 | March 2010 | September 2012 |
| MongoDB 1.2 | December 2009 | June 2011 |
Basic commands on mongo shell :
The following commands provides various examples for querying in the MongoDB shell.
- Connect with “admin login” to “admin database” :
$ mongo admin -u admin -p admin_password
- Show all available databases :
$ show dbs;
- Access to a particular database, e.g. testdb . This will create testdb if it does not already exist:
$ use testdb;
- Show all collections in the database :
$ show collections;
- Create a new collection :
$ db.createCollection('newCollection');
- Insert document into the newCollection created above :
$ db.newCollection.insertOne({name:'Yad',age:'25'});
Operators on mongo shell :
The following operators are using for querying in the MongoDB shell :
| Operator | Use | Example |
|---|---|---|
| $eq | Check if the value is equal | {age:{$eq:20}} |
| $lt | Check if value is less than | {age: {$lt:20}} |
| $gte | Check if value is greater than or equal to | {age:{$gte:22}} |
| $lte | Check if value is less thank or equal to | {age:{$lte:22}} |
- Example :
$ db.newCollection.find({age:{$gt:20}});
{ "_id" : ObjectId("7b5c29a715b06e5e783d8453"), "name" : "Yad", "age" : 25 }
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I hope now you know what MongoDB looks like, how documents are different compared to a typical relational database record, and you are able to do some manipulation on your MongoDB database.Â
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Founder of RakDBA.com
Expert database administrator on Oracle & SQL Server databases with 10 years experience. Certified OCA for Oracle and MSCP for SQL SERVER 2012 administration.