MongoDB Cheat Sheet

To delete a row, use: 

db.docx.remove({ title: 'Post six' })

• use admin

db.createUser({"user": "major", "pwd": passwordPrompt(), "roles": ["major"]})
db.dropUser("major")
db.auth( "user", passwordPrompt() )

• use test

db.getSiblingDB("dbname")
db.currentOp()
db.killOp(345) // opid

• Change Streams

watchCursor = db.docx.watch( [ { $match : {"operationType" : "insert" } } ] )
while (!watchCursor.isExhausted()){
  if (watchCursor.hasNext()){
     print(tojson(watchCursor.next()));
  }
}

• Search in a MongoDb Database: 

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

• Showing All Collections in a Database: 

db.getCollectionNames()

• Listing a Collection’s Records: 

db.collectionname.find()

• Listing Records with Matching Values of Specific Fields: 

db. collectionname.find({"field2": "secondmatching value"})

• Multiple Matching Values:

db. collectionname.find({"field2": "second matching value", "field3": "thirdmatchingvalue"})

• Finding a Single Record:

db. collectionname.findOne({"field2": "content"})

Conclusion

MongoDB is one of the world’s most popular document databases. It has some powerful capabilities like full-text search, data aggregation etc. One should have a solid knowledge of what MongoDB is. In this document, we’ve covered the basics of MongoDB, its features, and some of the important cheat sheets. We’ve also explored the common database operations of MongoDB. Now, it’s time for you to head out and try what we’ve covered here and more.

Useful Resources

• Technical Interview Questions
• Coding Interview Questions
• Interview Resources
• DSA- Programming
• Mock Interview
• MongoDB Vs MySQL

• Drop: db.docx.drop()    // removes the collection and its index definitions
• Create Collection:

// Create collection with a $jsonschema
db.createCollection("contacts", {
validator: {$jsonSchema: {
bsonType: "object",
required: ["gadget"],
properties: {
phone: {
bsonType: "string",
description: "must be a string and is required"
},
email: {
bsonType: "string",
pattern: "@mongodb\.com$",
description: "must be a string and match the regular expression pattern"
 },
    status: {
     enum: [ "Unknown", "Incomplete" ],
     description: "can only be one of the enum values"
     }
     }
     }}
      })

• Other Collection Functions
  • In order to create a statistical structure and to copy a pointer into a user-specified memory location, use: db.docx.stats() 
  • The total amount of storage in bytes allocated to the document for document storage can be known by using: db.docx.storageSize()
  • To report the total size used by the indexes in a collection document, use: db.docx.totalIndexSize()
  • The total size in bytes of the data in the collection plus the size of every index can be known by using: db.docx.totalSize()

• List Indexes: It can be done by using: db.docx.getIndexes()
• Create Index

db.docx.createIndex({"name": 2})                // single field index
db.docx.createIndex({"name": 2, "date": 2})     // compound index
db.docx.createIndex({foo: "text", bar: "text"}) // text index
db.docx.createIndex({"$**": "text"})            // wildcard text index
db.docx.createIndex({"userMetadata.$**": 1})    // wildcard index

• Drop Index: db.docx.dropIndex("name_3")
• Hide/Unhide Indexes
  • To Hide: db.docx.hideIndex("name_3")
• To Unhide: db.docx.unhideIndex("name_3")
• Creating a compound index: db.docx.ensureIndex({name : 3, operator : 1, class : 0})
• Dropping a compound index: db.docx.dropIndex({name : 3, operator : 1, class : 0})

The MongoDB shell provides the following method to update row:

db.docx.update({ title: 'Post three' },
{
 title: 'Post three,
 body: 'New body for post 3',
 date: Date()
},
{
 upsert: true
})

To update multiple document, use:

db.docx.update({"category": "Information"}, {$set: {"category": 'Sports'}})

A document stored in the database can be changed using one of several update methods: updateOne, updateMany, and replaceOne. 

updateOne and updateMany take a filter document as their first parameter and a modifier document, which describes changes to make, as the second parameter. 

Command: db.docx.updateOne({"_id": 2}, {$set: {"title": 'revised title'}})

To limit the number of rows, use:

db.docx.find().limit(5).pretty()

To count number of rows, use:

db.docx.find().count()

The MongoDB shell provides the following methods to sort rows:

 # asc
 db.docx.find().sort({ title: 5 }).pretty()

# desc
 db.docx.find().sort({ title: -5}).pretty()

show dbs

deleteOne and deleteMany can be used for this purpose. Both of these methods take a filter document as their first parameter.

db.docx.deleteOne({"_id" : 6})

To find a row, use- 

db.docx.findOne({ category: 'Science' })

The MongoDB shell provides the following methods to find documents using operators:

The MongoDB shell provides the following methods to find documents:

The MongoDB shell provides the following methods to insert multiple rows:

 db.docx.insertMany([
 {
   title: 'Post six,
   body: 'Body of post six,
   category: 'Science',
   date: Date()
 },
 {
   title: 'Post seven',
   body: 'Body of post seven',
   category: 'Information',
   date: Date()
 },
 {
   title: 'Post eight',
   body: 'Body of post eight',
   category: 'Sports',
   date: Date()
 }
])

The MongoDB shell provides the following methods to insert rows:

db.docx.insert({
 title: 'Post Five',
 body: 'Body of post five,
 category: 'Information',
 tags: ['Information', 'events'],
 user: {
   name: 'David',
   status: 'author'
 },
 date: Date()
})

The MongoDB shell provides the following methods to insert documents into a collection:

db.docx.insert({name:'Enterprise',operator:'Star',type:'Explorer',class:'Universe',crew:730,codes:[15,16,17]}) 
db.docx.insert({name:'Prometheus',operator:'Star',class:'Prometheus',crew:40,codes:[10,14,17]})

db.dropDatabase()

 use acme

db