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Dmitry Romanoff
Dmitry Romanoff

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12 Useful MongoDB Commands Every Developer Should Know

#mongodb #database #json #programming

MongoDB is a powerful NoSQL database, and while it’s easy to get started, having a good handle on some basic commands can save you time and help you understand your data better.

Here are 12 essential MongoDB commands that I find incredibly useful for everyday database management, querying, and development tasks.

1. show databases

Lists all available databases on your MongoDB server.

rs0 [direct: primary] test> show databases
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Example Output:

dima_database_1 48.00 KiB newdatabase 1.45 MiB newdatabase_copy 1.41 MiB sample_database 32.00 KiB stressTestDB 34.64 MiB test 128.00 KiB test_db 18.16 MiB testdb 32.00 KiB
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2. use mydatabase

Switch to the specified database. If it doesn’t exist, MongoDB will create it once you insert data.

use newdatabase
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Output:

switched to db newdatabase
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3. show collections

Displays all collections (similar to tables in SQL) in the current database.

rs0 [direct: primary] newdatabase> show collections
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Output:

collection_1 collection_10 collection_2 ...
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4. db.collection.countDocuments()

Returns the number of documents in a collection.

db.collection_1.countDocuments()
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Output:

500
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5. db.collection.find().limit(n).forEach(printjson)

Prints the first n documents from a collection in a readable JSON format.

db.collection_1.find().limit(3).forEach(printjson);
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Output:

{ _id: ObjectId("686ba3cd8d1e2b93aec59f35"), name: "Item_0", value: 767, created_at: ISODate("2025-07-07T10:39:08.904Z") } ...
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6. Custom Formatted Output with forEach

This version prints documents with custom formatting for easier visual scanning.

db.collection_1.find().limit(3).forEach(function(doc) { const id = (doc._id && doc._id.str) ? doc._id.str.substring(0, 6) : "------"; const name = doc.name ? doc.name.toString().padEnd(10) : "N/A".padEnd(10); const value = (doc.value !== undefined) ? doc.value.toString().padStart(5) : " N/A"; const date = (doc.created_at && doc.created_at.toISOString) ? doc.created_at.toISOString().substr(0, 19) : "no-date"; print(id + "\t" + name + "\t" + value + "\t" + date); });
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Output:

------ Item_0 767 2025-07-07T10:39:08 ------ Item_1 763 2025-07-07T10:39:09 ------ Item_2 601 2025-07-07T10:39:09
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7. Filtered Count with Regex

Count documents where the name field starts with "Item".

db.collection_1.countDocuments({ name: /^Item/ })
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Output:

500
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8. deleteMany with $in Filter

Delete specific documents based on matching values.

db.collection_1.deleteMany({ name: { $in: ["Item_20", "Item_25"] } });
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Output:

{ acknowledged: true, deletedCount: 2 }
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9. insertMany to Add Documents

Add multiple new documents at once.

db.collection_1.insertMany([ { name: "Item_234", value: 234, created_at: new Date() }, { name: "Item_345", value: 345, created_at: new Date() }, { name: "Item_456", value: 456, created_at: new Date() } ]);
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Output:

{ acknowledged: true, insertedIds: { '0': ObjectId("686bb71a123fdce1b6c63238"), '1': ObjectId("686bb71a123fdce1b6c63239"), '2': ObjectId("686bb71a123fdce1b6c6323a") } }
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10. updateOne to Modify Documents

Update documents based on a condition.

db.collection_1.updateOne({ name: "Item_234" }, { $set: { name: "Item_2345" } }); db.collection_1.updateOne({ name: "Item_345" }, { $set: { name: "Item_3456" } }); db.collection_1.updateOne({ name: "Item_456" }, { $set: { name: "Item_4567" } });
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Output:

{ acknowledged: true, matchedCount: 1, modifiedCount: 1 }
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11. Aggregation with $group, $sort, $limit

Aggregate documents to see how many times each name occurs.

db.collection_1.aggregate([ { $group: { _id: "$name", count: { $sum: 1 } } }, { $sort: { count: -1 } }, { $limit: 5 } ]);
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Output:

[ { _id: "Item_4567", count: 2 }, { _id: "Item_3456", count: 2 }, { _id: "Item_2345", count: 2 }, { _id: "Item_451", count: 1 }, { _id: "Item_185", count: 1 } ]
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12. Drop the Entire Database

⚠️ Be careful with this one! This will delete the selected database.

use newdatabase db.dropDatabase()
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Output:

{ ok: 1, dropped: 'newdatabase' }
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🔚 Conclusion

These commands are essential building blocks when working with MongoDB, especially when interacting directly via the shell. Whether you're debugging, inspecting data, or performing CRUD operations, they’ll come in handy.

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