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Catalog / MongoDB Cheat Sheet

MongoDB Cheat Sheet

A quick reference guide to MongoDB commands, syntax, and operations for developers and database administrators.

Basic Operations

Connecting to MongoDB

Connect to a MongoDB instance using the mongo shell:

mongo

To connect to a specific host and port:

mongo --host <hostname> --port <port>

Connect to a MongoDB instance with authentication:

mongo -u <username> -p <password> --authenticationDatabase <db>

Database Operations

show dbs

Lists all the databases available on the server.

use <database_name>

Switches to the specified database. Creates the database if it doesn’t exist.

db

Displays the current database you are using.

db.dropDatabase()

Deletes the current database.

Collection Operations

show collections

Lists all collections in the current database.

db.createCollection('<collection_name>')

Creates a new collection in the current database.

db.<collection_name>.drop()

Deletes the specified collection.

CRUD Operations

Insert Operations

Insert a single document:

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

Insert multiple documents:

db.<collection_name>.insertMany([{ key: 'value' }, { key: 'value2' }])

Query Operations

Find all documents in a collection:

db.<collection_name>.find()

Find documents with a specific condition:

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

Find a single document that matches the condition:

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

Using operators:

db.<collection_name>.find({age: {$gt: 25}})

Update Operations

Update a single document:

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

Update multiple documents:

db.<collection_name>.updateMany({ query }, { $set: { key: 'new_value' } })

Replace a single document:

db.<collection_name>.replaceOne({ query }, { key: 'new_value' })

Delete Operations

Delete a single document:

db.<collection_name>.deleteOne({ query })

Delete multiple documents:

db.<collection_name>.deleteMany({ query })

Querying with Operators

Comparison Operators

$eq

Matches values that are equal to a specified value.

db.inventory.find( { qty: { $eq: 20 } } )

$gt

Matches values that are greater than a specified value.

db.inventory.find( { qty: { $gt: 20 } } )

$gte

Matches values that are greater than or equal to a specified value.

db.inventory.find( { qty: { $gte: 20 } } )

$lt

Matches values that are less than a specified value.

db.inventory.find( { qty: { $lt: 20 } } )

$lte

Matches values that are less than or equal to a specified value.

db.inventory.find( { qty: { $lte: 20 } } )

$ne

Matches all values that are not equal to a specified value.

db.inventory.find( { qty: { $ne: 20 } } )

$in

Matches any of the values specified in an array.

db.inventory.find( { qty: { $in: [ 5, 15 ] } } )

$nin

Matches none of the values specified in an array.

db.inventory.find( { qty: { $nin: [ 5, 15 ] } } )

Logical Operators

$and

Joins query clauses with a logical AND returns all documents that match the conditions of both clauses.

db.inventory.find( { $and: [ { price: { $ne: 1.99 } }, { qty: { $lt: 20 } }, { sale: true } ] } )

$or

Joins query clauses with a logical OR returns all documents that match the conditions of either clause.

db.inventory.find( { $or: [ { qty: { $lt: 20 } }, { price: { $gt: 10 } } ] } )

$not

Inverts the effect of a query expression and returns documents that do not match the query expression.

db.inventory.find( { price: { $not: { $gt: 1.99 } } } )

$nor

Joins query clauses with a logical NOR returns all documents that fail to match both clauses.

db.inventory.find( { $nor: [ { price: 1.99 }, { qty: { $lt: 20 } } ] } )

Element Operators

$exists

Matches documents that have the specified field.

db.inventory.find( { size: { $exists: true } } )

$type

Selects documents where values match a specified BSON type.

db.inventory.find( { qty: { $type: "number" } } )

Indexes and Aggregation

Index Operations

Create an index on a field:

db.<collection_name>.createIndex({ field: 1 })

(1 for ascending, -1 for descending)

List all indexes for a collection:

db.<collection_name>.getIndexes()

Drop an index:

db.<collection_name>.dropIndex('<index_name>')

Aggregation Pipeline

An example aggregation pipeline:

db.<collection_name>.aggregate([
  { $match: { status: "A" } },
  { $group: { _id: "$cust_id", total: { $sum: "$amount" } } },
  { $sort: { total: -1 } }
])

$match: Filters the documents to pass only the documents that match the specified condition(s) to the next stage in the pipeline.

$group: Groups documents that share the same _id.

$sort: Sorts all input documents and returns them to the pipeline in sorted order.

$project: Passes along the documents with the requested fields to the next stage in the pipeline. The specified fields can be existing fields or newly computed fields.

$limit: Limits the number of documents passed to the next stage in the pipeline.

$skip: Skips over the specified number of documents and passes the remaining documents to the next stage in the pipeline.
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