A-Z: MongoDB Cheat Sheet🌱

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Boost Your Programming Efficiency: Essential Tools for Success ⚙️

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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.

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MongoDB Shell Commands 🍃🌲

• Show Database

show dbs

This command will show all the databases in your MongoDB server.

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• Use Database

use <database_name>

This command will switch to the database you want to use.

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• Show Collections

show collections

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

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• Drop Database

db.dropDatabase()

This command will drop the database you are using.

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• Create Collection

db.createCollection("<collection_name>")

This command will create a collection in the database you are using.

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• Insert a Document

db.<collection_name>.insertOne({
    <key>: <value>,
    <key>: <value>,
    ...
})

This command will insert a document in the collection you are using.

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• Insert Multiple Documents

db.<collection_name>.insertMany([
    {
        <key>: <value>,
        <key>: <value>,
        ...
    },
    {
        <key>: <value>,
        <key>: <value>,
        ...
    },
    ...
])

This command will insert multiple documents in the collection you are using.

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• Find Documents

db.<collection_name>.find()

This command will find all the documents in the collection you are using.

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• Find Documents with Query

db.<collection_name>.find({
    <key>: <value>
})

This command will find all the documents in the collection you are using that match the query.

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• Count Documents

db.<collection_name>.find({
    <key>: <value>
    }).count()

This command will count all the documents in the collection you are using that match the query.

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• Limit Documents

db.<collection_name>.find().limit(<number>)

This command will limit the number of documents returned by the find command.

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• forEach()

db.<collection_name>.find().forEach(function(doc) {
    print("Key: " + doc.<key> + " Value: " + doc.<value>);
})

This command will iterate through all the documents in the collection you are using and print the key and value of each document.

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• Find One Document

db.<collection_name>.findOne({
    <key>: <value>
})

This command will find the first document in the collection you are using that matches the query.

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• Update a Document

db.<collection_name>.updateOne({
    <key>: <value>
}, {
    $set: {
        <key>: <value>
    }
})

This command will update the first document in the collection you are using that matches the query. $set is used to update the document.

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• Increment a Document

db.<collection_name>.updateOne({
    <key>: <value>
}, {
    $inc: {
        <key>: <value>
    }
})

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.

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• Delete a Document

db.<collection_name>.deleteOne({
    <key>: <value>
})

This command will delete the first document in the collection you are using that matches the query.

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• Add new field to a Document

db.<collection_name>.updateOne({
    <key>: <value>
}, {
    $set: {
        <new_key>: <new_value>
    }
})

This command will add a new field to the first document in the collection you are using that matches the query.

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• Greater than

db.<collection_name>.find({
    <key>: {
        $gt: <value>
    }
})

This command will find all the documents in the collection you are using that have a key greater than the value.

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• Greater than or equal to

db.<collection_name>.find({
    <key>: {
        $gte: <value>
    }
})

This command will find all the documents in the collection you are using that have a key greater than or equal to the value.

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• Less than

db.<collection_name>.find({
    <key>: {
        $lt: <value>
    }
})

This command will find all the documents in the collection you are using that have a key less than the value.

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• Less than or equal to

db.<collection_name>.find({
    <key>: {
        $lte: <value>
    }
})

This command will find all the documents in the collection you are using that have a key less than or equal to the value.

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• Not equal to

db.<collection_name>.find({
    <key>: {
        $ne: <value>
    }
})

This command will find all the documents in the collection you are using that have a key not equal to the value.

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• And

db.<collection_name>.find({
    $and: [
        {
            <key>: <value>
        },
        {
            <key>: <value>
        }
    ]
})

This command will find all the documents in the collection you are using that match the query.

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• Or

db.<collection_name>.find({
    $or: [
        {
            <key>: <value>
        },
        {
            <key>: <value>
        }
    ]
})

This command will find all the documents in the collection you are using that match the query.

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• Sort

db.<collection_name>.find().sort({
    <key>: <value>
})

This command will sort all the documents in the collection you are using by the key.

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• Sort Descending

db.<collection_name>.find().sort({
    <key>: -1
})

This command will sort all the documents in the collection you are using by the key in descending order.

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• Drop Collection

db.<collection_name>.drop()

This command will drop the collection you are using.

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Thank You 🌿🌴🌲

Thanks for reading! I hope you found this useful. If you have any questions or feedback.
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References

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