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Burak Boduroğlu
Burak Boduroğlu

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A-Z: MongoDB Cheat Sheet🌱

#mongodb #webdev #javascript #tutorial

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Contents 📖

Definitions 🌳

  • What is MongoDB?

MongoDB is a document database with the scalability and flexibility that you want with the querying and indexing that you need.

  • What is a Database?

A database holds a set of collections. A database typically has a separate file system directory to hold its data. Each database gets its own set of files on the file system. Generally, you associate a database with one application.

  • What is a Collection?

A collection is a group of documents. If a document is the MongoDB analog of a row in a relational database table, then a collection is the analog of a table.

  • What is a Document?

A record in MongoDB is a document, which is a data structure composed of field and value pairs. MongoDB documents are similar to JSON objects. The values of fields may include other documents, arrays, and arrays of documents.

  • What is a Field?

A document has a dynamic schema. Dynamic schemas allow documents in the same collection to have different sets of fields and to have different field names for the common fields.

  • What is a Primary Key?

In MongoDB, each document stored in a collection requires a unique _id field that acts as a primary key. If an inserted document omits the _id field, the MongoDB driver automatically generates an ObjectId for the _id field.

  • Why use NoSQL?

NoSQL databases are built to allow the insertion of data without a predefined schema. This makes NoSQL databases ideal for storing and processing unstructured data.

  • Why use MongoDB?

MongoDB is a document database, which means it stores data in JSON-like documents. We believe this is the most natural way to think about data, and is much more expressive and powerful than the traditional row/column model.

MongoDB Shell Commands 🍃🌲

  • Show Database 
show dbs
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This command will show all the databases in your MongoDB server.

  • Use Database 
use <database_name>
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This command will switch to the database you want to use.

  • Show Collections 
show collections
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This command will show all the collections in the database you are using.

  • Drop Database 
db.dropDatabase()
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This command will drop the database you are using.

  • Create Collection 
db.createCollection("<collection_name>")
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This command will create a collection in the database you are using.

  • Insert a Document 
db.<collection_name>.insertOne({
    <key>: <value>,
    <key>: <value>,
    ...
})
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This command will insert a document in the collection you are using.

  • Insert Multiple Documents 
db.<collection_name>.insertMany([
    {
        <key>: <value>,
        <key>: <value>,
        ...
    },
    {
        <key>: <value>,
        <key>: <value>,
        ...
    },
    ...
])
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This command will insert multiple documents in the collection you are using.

  • Find Documents 
db.<collection_name>.find()
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This command will find all the documents in the collection you are using.

  • Find Documents with Query 
db.<collection_name>.find({
    <key>: <value>
})
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This command will find all the documents in the collection you are using that match the query.

  • Count Documents 
db.<collection_name>.find({
    <key>: <value>
    }).count()
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This command will count all the documents in the collection you are using that match the query.

  • Limit Documents 
db.<collection_name>.find().limit(<number>)
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This command will limit the number of documents returned by the find command.

  • forEach() 
db.<collection_name>.find().forEach(function(doc) {
    print("Key: " + doc.<key> + " Value: " + doc.<value>);
})
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This command will iterate through all the documents in the collection you are using and print the key and value of each document.

  • Find One Document 
db.<collection_name>.findOne({
    <key>: <value>
})
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This command will find the first document in the collection you are using that matches the query.

  • Update a Document 
db.<collection_name>.updateOne({
    <key>: <value>
}, {
    $set: {
        <key>: <value>
    }
})
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This command will update the first document in the collection you are using that matches the query. $set is used to update the document.

  • Increment a Document 
db.<collection_name>.updateOne({
    <key>: <value>
}, {
    $inc: {
        <key>: <value>
    }
})
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This command will increment the value of the key in the first document in the collection you are using that matches the query. $inc is used to increment the value of the key.

  • Delete a Document 
db.<collection_name>.deleteOne({
    <key>: <value>
})
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This command will delete the first document in the collection you are using that matches the query.

  • Add new field to a Document 
db.<collection_name>.updateOne({
    <key>: <value>
}, {
    $set: {
        <new_key>: <new_value>
    }
})
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This command will add a new field to the first document in the collection you are using that matches the query.

  • Greater than 
db.<collection_name>.find({
    <key>: {
        $gt: <value>
    }
})
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This command will find all the documents in the collection you are using that have a key greater than the value.

  • Greater than or equal to 
db.<collection_name>.find({
    <key>: {
        $gte: <value>
    }
})
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This command will find all the documents in the collection you are using that have a key greater than or equal to the value.

  • Less than 
db.<collection_name>.find({
    <key>: {
        $lt: <value>
    }
})
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This command will find all the documents in the collection you are using that have a key less than the value.

  • Less than or equal to 
db.<collection_name>.find({
    <key>: {
        $lte: <value>
    }
})
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This command will find all the documents in the collection you are using that have a key less than or equal to the value.

  • Not equal to 
db.<collection_name>.find({
    <key>: {
        $ne: <value>
    }
})
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This command will find all the documents in the collection you are using that have a key not equal to the value.

  • And 
db.<collection_name>.find({
    $and: [
        {
            <key>: <value>
        },
        {
            <key>: <value>
        }
    ]
})
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This command will find all the documents in the collection you are using that match the query.

  • Or 
db.<collection_name>.find({
    $or: [
        {
            <key>: <value>
        },
        {
            <key>: <value>
        }
    ]
})
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This command will find all the documents in the collection you are using that match the query.

  • Sort 
db.<collection_name>.find().sort({
    <key>: <value>
})
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This command will sort all the documents in the collection you are using by the key.

  • Sort Descending 
db.<collection_name>.find().sort({
    <key>: -1
})
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This command will sort all the documents in the collection you are using by the key in descending order.

  • Drop Collection 
db.<collection_name>.drop()
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This command will drop the collection you are using.

Thank You 🌿

Thank you for taking the time to read my blog post! I hope you found it helpful and informative. Your support and engagement mean a lot to me. If you have any questions or feedback, please don’t hesitate to reach out. I appreciate your continued interest and look forward to sharing more valuable content in the future. Thank you once again!

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Top comments (26)

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imthedeveloper profile image
ImTheDeveloper •

Nice overview. Loved mongo for very simple document storage where there is little to no need to do any complex joins. It can become a beast when needing to use the aggregation pipeline and transformations I've walked into that a couple of times now and wished I'd have stuck to something more relational. My own fault and lesson learnt 🤣 again though really nice overview and covers so many use cases.

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prsaya profile image
Prasad Saya •

The document data of MongoDB is like JSON (plus has more types) and it includes complex types like objects and arrays, often nested to multiple levels (upto 100 levels is possible as per the docs). Working with these complex structures is not always easy. First, the aggregation pipeline syntax is unlike other database querying syntax and there is a learning curve. Attempting aggregation queries on complex data and complex operations without proper learning, the tools and experience is not uncommon - it can create disappointments.

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burakboduroglu profile image
Burak Boduroğlu •

🤩🥳

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umakantv profile image
Umakant Vashishtha •

This is helpful, I wrote a similar article:
umakantv.medium.com/mongodb-operat... with more types of operators and an example which demonstrates fuzzy text search.

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burakboduroglu profile image
Burak Boduroğlu •

Thank you. It looks like helpful.😊

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michaeltharrington profile image
Michael Tharrington •

Awesome post here, Burak! This is a really helpful and easy-to-read cheat sheet. 🙌

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burakboduroglu profile image
Burak Boduroğlu •

I am happy to It was useful. Thank you. 🥳

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prsaya profile image
Prasad Saya •

Good effort 👍.

I would also include the variations of update and delete methods updateMany and deleteMany. Also, countDocuments is useful.

One of the more useful features of using MongoDB is one can develop applications fast, as it allows quick start and prototyping (for example, I can write application code accessing the database and insert data, query it, etc., without creating a database or a collection, and fields explicitly).

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billernet profile image
Bill💡 •

Good stuff. We replaced our legacy XML based document format with MongoDB and saw massive speed improvements in loading and querying data. I'm a big proponent of dealing with documents with large volume/size/complexity this way. One thing I would take issue with though is this:

  • Why use MongoDB?

MongoDB is a document database, which means it stores data in JSON-like documents. We believe this is the most natural way to think about data, and is much more expressive and powerful than the traditional row/column model.

While yes, it probably does let you store data in exactly the format that represents the original document, I think it is worth stating that it shouldn't be seen as a wholesale replacement for relational databases. A good rule of thumb is if to use MongoDB or any other document database, and you're finding that the document is starting to contain items which are outside the natural scope of the document to get it to work, it is not a good fit.

Define boundaries for what is stored in the document and be aware of the limitations of relationships between documents.

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burakboduroglu profile image
Burak Boduroğlu •

Thanks for sharing this nice comment.😊

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boly38 profile image
Brice •

Good idea 👍🏻

Improvement idea:
From industrialization point of view
When I do update the mongo part of my application I check every possible queries from repository classes and check fields used to build indexes and avoid perf Issues.
You could maybe add a section about indexes and explain plans.

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burakboduroglu profile image
Burak Boduroğlu •

Thanks for your recommendation. I’m going to add this section. 😇

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onlinemsr profile image
Raja MSR •

Thank you for sharing this useful MongoDB cheat sheet. I found it very helpful and concise. It covers the most common commands and operations for working with MongoDB databases.

I appreciate your effort and time in creating this resource!

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burakboduroglu profile image
Burak Boduroğlu •

👾👨🏻‍💻🙏🏼

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faisal00121 profile image
Cloudrcm Solutions •

Great MongoDB cheat sheet! It's always helpful to have a quick reference guide to assist with common tasks and commands in MongoDB. As someone interested in cloud RCM (Revenue Cycle Management), I can see the potential benefits of integrating MongoDB into cloud-based RCM systems.

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burakboduroglu profile image
Burak Boduroğlu •

Thanks for your comment.😊

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araaranomi profile image
Ara Ara no Mi •

I still don't have any usecases for MongoDB, all the data I use ends up being Relational, and I prefer SQL's syntax.

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kumarkalyan profile image
Kumar Kalyan •

Great reasource for mongo db :)

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burakboduroglu profile image
Burak Boduroğlu •

Thank you :) 👾

View full discussion (26 comments)

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