MongoDb Cheatsheet

"In this post, we will see a comprehensive list of all the mongodb commands you will ever need as a mongoDb beginner. This list covers almost all the mostly used commands in mongoDb."

A comprehensive list of the most commonly used MongoDB commands for beginners (compatible with MongoDB 4.2, 5.x, 6.x, and 7.x). Assume we are working in a collection named comments in a database of your choice.

1. Database Commands

View all databases

show dbs

Create a new or switch databases

use dbName

View current database

db

Delete current database

db.dropDatabase()

2. Collection Commands

Show collections

show collections

Create a collection named 'comments'

db.createCollection('comments')

Drop a collection named 'comments'

db.comments.drop()

3. Document (Row) Commands

Show all documents in a collection

db.comments.find()

Show all documents (pretty format)

db.comments.find().pretty()

Find the first document matching a filter

db.comments.findOne({name: 'Harry'})

Insert one document

db.comments.insertOne({
    name: 'Harry',
    lang: 'JavaScript',
    member_since: 5
})

Insert many documents

db.comments.insertMany([
    {name: 'Harry', lang: 'JavaScript', member_since: 5}, 
    {name: 'Rohan', lang: 'Python', member_since: 3},
    {name: 'Lovish', lang: 'Java', member_since: 4}
])

Search by field

db.comments.find({lang: 'Python'})

Limit the number of results

db.comments.find().limit(2)

Skip results (useful for pagination)

db.comments.find().skip(2).limit(2)

Count the number of matching documents

db.comments.countDocuments({lang: 'Python'})

4. Update Commands

Update one document

db.comments.updateOne(
    {name: 'Shubham'},
    {$set: {name: 'Harry', lang: 'JavaScript', member_since: 51}},
    {upsert: true}
)

Update many documents

db.comments.updateMany(
    {lang: 'JavaScript'},
    {$set: {verified: true}}
)

Increment a field

db.comments.updateOne(
    {name: 'Rohan'},
    {$inc: {member_since: 2}}
)

Rename a field

db.comments.updateOne(
    {name: 'Rohan'},
    {$rename: {member_since: 'member'}}
)

5. Delete Commands

Delete one document

db.comments.deleteOne({name: 'Harry'})

Delete many documents

db.comments.deleteMany({lang: 'Java'})

6. Query Operators

Comparison Operators

db.comments.find({member_since: {$lt: 90}})   // less than
db.comments.find({member_since: {$lte: 90}})  // less than or equal
db.comments.find({member_since: {$gt: 90}})   // greater than
db.comments.find({member_since: {$gte: 90}})  // greater than or equal
db.comments.find({member_since: {$ne: 5}})    // not equal

Logical Operators

db.comments.find({$and: [{lang: 'Python'}, {member_since: {$gt: 2}}]})
db.comments.find({$or: [{lang: 'Python'}, {lang: 'Java'}]})
db.comments.find({lang: {$in: ['Python', 'Java']}})
db.comments.find({lang: {$nin: ['C++', 'Rust']}})

Sorting

db.comments.find().sort({member_since: 1})   // ascending
db.comments.find().sort({member_since: -1})  // descending

Projection (select specific fields)

db.comments.find({}, {name: 1, lang: 1, _id: 0})

7. Indexes (Basics)

Create an index

db.comments.createIndex({name: 1})

View indexes

db.comments.getIndexes()

Drop an index

db.comments.dropIndex({name: 1})

8. Aggregation (Basics)

Count by field

db.comments.aggregate([
  {$group: {_id: "$lang", total: {$sum: 1}}}
])

Average by field

db.comments.aggregate([
  {$group: {_id: "$lang", avgExperience: {$avg: "$member_since"}}}
])

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