#_ the Mongodb Ultimate [ Cheat Sheet ]

1. Setup & Management:

● mongod: Start the MongoDB server.

● mongo: Connect to a running MongoDB server.
● mongos: Start a mongos server for sharding.
● mongodump: Backup MongoDB database.
● mongorestore: Restore MongoDB database from backup.
● mongoexport: Export a collection to JSON or CSV.
● mongoimport: Import content from JSON or CSV into a collection.

2. Basic Shell Commands:

● show dbs: List all databases.

● use <dbname>: Switch to database or create it if it doesn't exist.
● show collections: List all collections in the current database.
● db.help(): Display help for MongoDB commands in the shell.

3. CRUD Operations:

● db.collection.insert(document): Insert a document.

● db.collection.find(): Retrieve documents.
● db.collection.update(criteria, changes): Update documents.
● db.collection.delete(criteria): Delete documents.
● db.collection.save(document): Update an existing document or
insert a new one.
● db.collection.replaceOne(filter, replacement): Replace a document.

4. Querying:

● db.collection.find({field: value}): Query by specific field value.

● db.collection.find({field: {$gt: value}}): Query for documents
where field value is greater than a specified value.
● db.collection.find().sort({field: 1}): Sort query results in
ascending order by field.
● db.collection.find().limit(n): Limit query results to n documents.

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 ● db.collection.find().skip(n): Skip the first n results of a query.
● db.collection.findOne(): Retrieve a single document.
● db.collection.count(): Count documents that match a query.

5. Advanced Queries:

● db.collection.find({$or: [{field1: value1}, {field2: value2}]}):

Query using the OR condition.
● db.collection.find({field: {$in: [value1, value2, ...]}}): Query
where field value is in the specified array.
● db.collection.find({field: {$exists: true/false}}): Query documents
where a field does or doesn't exist.
● db.collection.find({field: {$type: BSONType}}): Query by BSON type.

6. Aggregation:

● db.collection.aggregate(): Process data and return computed

results.
● $group: Group by some specified expression.
● $sort: Sort documents.
● $limit: Limit the number of documents.
● $skip: Skip specified number of documents.
● $unwind: Deconstructs an array field.

7. Indexing:

● db.collection.createIndex({field: 1}): Create an index on a field.

● db.collection.getIndexes(): List all indexes on a collection.
● db.collection.dropIndex(indexName): Remove an index.
● db.collection.reIndex(): Rebuild indexes.

8. Administration:

● db.runCommand({commandName: 1}): Run a database command.

● db.dropDatabase(): Drop the current database.
● db.collection.drop(): Drop a collection.
● db.collection.stats(): Returns statistics about the collection.

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9. Replication:

● rs.initiate(): Initialize a new replica set.

● rs.add(host): Add a member to the replica set.
● rs.status(): View the status of the replica set.
● rs.conf(): View the replica set's configuration.
● rs.remove(host): Remove a member from the replica set.

10. Sharding:

● sh.status(): Show sharding status.

● sh.addShard(shardURL): Add a shard to a cluster.
● sh.enableSharding(database): Enable sharding for a database.
● sh.shardCollection(namespace, key): Enable sharding for a
collection.

11. Monitoring & Diagnostics:

● mongostat: Provide statistics about MongoDB's state.

● mongotop: Monitor read/write activity on a per-collection level.
● db.serverStatus(): Retrieve server status.
● db.currentOp(): Show in-progress operations.
● db.killOp(opid): Kill a specific operation.

12. User and Role Management:

● db.createUser(userDocument): Create a new user.

● db.dropUser(username): Delete a user.
● db.updateUser(username, fields): Update user data.
● db.createRole(roleDocument): Create a new role.
● db.dropRole(roleName): Delete a role.

13. Security & Authentication:

● --auth: Start MongoDB with authentication.

● db.auth(username, password): Authenticate a user.
● --sslMode requireSSL: Start MongoDB with SSL.

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14. Storage:

● --storageEngine wiredTiger: Specify the WiredTiger storage engine.

● db.collection.storageSize(): Retrieve the storage size for a
collection.
● db.collection.totalSize(): Retrieve the total size of a collection
including all indexes.

15. Backup & Restore:

● mongodump --db mydb: Backup a specific database.

● mongorestore --dir /path/to/backup: Restore from a specific backup
directory.

16. Import & Export:

● mongoexport --collection mycol --out mycol.json: Export a

collection to JSON.
● mongoimport --collection mycol --file mycol.json: Import a
collection from JSON.

17. Utilities:

● db.fsyncLock(): Lock a mongod instance for maintenance.

● db.fsyncUnlock(): Unlock a mongod instance.

18. Text Search:

● db.collection.createIndex({field: "text"}): Create a text index.

● db.collection.find({$text: {$search: "query"}}): Perform a text
search.

19. GridFS:

● mongofiles: Utility for putting and getting files from MongoDB

GridFS.
● db.fs.files.find(): Find files stored in GridFS.

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20. Miscellaneous Commands & Concepts:

● $elemMatch: Query for array elements.

● $upsert: Insert a new document if no document matches the query
criteria.
● $set: Set the value of a field.
● $unset: Remove a field.
● $push: Append a value to an array.
● $pop: Remove the first or last element of an array.
● $addToSet: Add a value to an array unless it already exists.
● db.collection.explain(): Explain a query.
● db.collection.distinct(field): Find distinct values for a field.
● db.collection.mapReduce(map, reduce, options): Perform a map-reduce
operation.
● ObjectId(): Create a new ObjectId.
● db.printReplicationInfo(): Print replication info.
● db.printShardingStatus(): Print sharding info.

21. Advanced Features & Options:

● db.runCommand({collMod: "collection", usePowerOf2Sizes: true}):

Modify collection options.
● db.collection.isCapped(): Check if a collection is capped.
● --oplogSize: Set the oplog size.
● --replSet "rsname": Start mongod as a member of replica set
"rsname".
● db.setProfilingLevel(level): Set the database profiling level.
● db.getProfilingStatus(): Check the database profiling status.
● db.collection.aggregate([{ $lookup: options }]): Left outer join of
two collections.
● --bind_ip: Bind MongoDB to listen to a specific IP address.
● --fork: Run MongoDB in the background.
● --logpath: Specify the log file path.

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22. Troubleshooting & Help:

● db.getLastError(): Return the error message from the last

operation.
● db.printSlaveReplicationInfo(): Print status of all replica set
members.
● mongo --help: Display help about command line options.
● db.getCollection("collection").help(): Display help on collection
methods.

23. Connection & Networking:

● --port: Specify the port number for MongoDB to listen on.

● db.getMongo(): Returns the current connection instance.
● db.getMongo().setReadPref("secondary"): Set read preference to
secondary nodes.
● db.getMongo().setSlaveOk(): Allows queries on replica set
secondaries.

24. Diagnostic Commands:

● db.collection.validate(): Validates the structure of data.

● db.runCommand({whatsmyuri: 1}): Returns the client's connection
string.
● db.hostInfo(): Provides details about the system MongoDB is
running on.
● db.collection.getShardDistribution(): Shows data distribution among
shards.

25. Schema Design:

● db.createCollection("name", options): Explicitly creates a

collection with options.
● db.collection.isCapped(): Determines if a collection is a capped
collection.
● $jsonSchema: Allows you to specify schema validation in the
collection level.

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26. Advanced Aggregation:

● $lookup: Joins documents from another collection.

● $graphLookup: Performs recursive search on a collection.
● $facet: Processes multiple aggregation pipelines within a single
stage.
● $bucket: Categorizes incoming documents into specific ranges.
● $bucketAuto: Categorizes incoming documents into a specified number
of equally sized ranges.

27. Concurrency & Transactions:

● db.beginTransaction(): Starts a multi-document transaction.

● db.commitTransaction(): Commits the active transaction.
● db.abortTransaction(): Aborts the active transaction.

28. Maintenance & Clean-up:

● db.repairDatabase(): Repairs the current database. Use with

caution as this can be blocking and lengthy.
● db.compactCollection(): Compacts a collection, reducing storage
use.
● db.collection.reIndex(): Rebuilds all indexes on a collection.

29. BSON Types & Handling:

● ObjectId("string"): Creates an ObjectId from the given string.

● $binary: Represents binary data.
● $date: Represents a specific date.
● $timestamp: Represents a BSON timestamp value.

30. Geospatial Queries:

● db.collection.createIndex({location: "2d"}): Creates a 2D

geospatial index.
● $near: Returns geospatial objects closest to a point.
● $geoWithin: Returns objects within a certain geospatial shape.

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31. TTL (Time-To-Live) Collections:

● db.collection.createIndex({field: 1}, {expireAfterSeconds:

seconds}): Sets up a TTL index which automatically removes
documents after a certain time.

32. Miscellaneous:

● db.setLogLevel(level): Changes the log level.

● $redact: Reshapes each document in the stream by restricting the
content for each document based on information stored in the
documents themselves.
● $merge: Writes the results of the aggregation pipeline to a
specified collection.
● db.getReplicaSetStatus(): Returns the status of the replica set
from the POV of the server it's run on.
● db.setFeatureCompatibilityVersion("version"): Sets the feature
compatibility version of MongoDB.

By: Waleed Mousa