MongoDB Cheat Sheet

mongodb_cheat_sheet.md

MongoDB Cheat Sheet

Show All Databases

show dbs

Show Current Database

db

Create Or Switch Database

use acme

Drop

db.dropDatabase()

Create Collection

db.createCollection('posts')

Show Collections

show collections

Insert Document

db.posts.insert({
  title: 'Post One',
  body: 'Body of post one',
  category: 'News',
  tags: ['news', 'events'],
  user: {
    name: 'John Doe',
    status: 'author'
  },
  date: Date()
})

Insert Multiple Documents

db.posts.insertMany([
  {
    title: 'Post Two',
    body: 'Body of post two',
    category: 'Technology',
    date: Date()
  },
  {
    title: 'Post Three',
    body: 'Body of post three',
    category: 'News',
    date: Date()
  },
  {
    title: 'Post Four',
    body: 'Body of post three',
    category: 'Entertainment',
    date: Date()
  }
])

Get All Documents

db.posts.find()

Get All Documents Formatted

db.posts.find().pretty()

Find Documents

db.posts.find({ category: 'News' })

Sort Documents

# asc
db.posts.find().sort({ title: 1 }).pretty()
# desc
db.posts.find().sort({ title: -1 }).pretty()

Count Documents

db.posts.find().count()
db.posts.find({ category: 'news' }).count()

Limit Documents

db.posts.find().limit(2).pretty()

Chaining

db.posts.find().limit(2).sort({ title: 1 }).pretty()

Foreach

db.posts.find().forEach(function(doc) {
  print("Blog Post: " + doc.title)
})

Find One Document

db.posts.findOne({ category: 'News' })

Find Specific Fields

db.posts.find({ title: 'Post One' }, {
  title: 1,
  author: 1
})

Update Document

db.posts.update({ title: 'Post Two' },
{
  title: 'Post Two',
  body: 'New body for post 2',
  date: Date()
},
{
  upsert: true
})

Update Specific Field

db.posts.update({ title: 'Post Two' },
{
  $set: {
    body: 'Body for post 2',
    category: 'Technology'
  }
})

Increment Field ($inc)

db.posts.update({ title: 'Post Two' },
{
  $inc: {
    likes: 5
  }
})

Rename Field

db.posts.update({ title: 'Post Two' },
{
  $rename: {
    likes: 'views'
  }
})

Delete Document

db.posts.remove({ title: 'Post Four' })

Sub-Documents

db.posts.update({ title: 'Post One' },
{
  $set: {
    comments: [
      {
        body: 'Comment One',
        user: 'Mary Williams',
        date: Date()
      },
      {
        body: 'Comment Two',
        user: 'Harry White',
        date: Date()
      }
    ]
  }
})

Find By Element in Array ($elemMatch)

db.posts.find({
  comments: {
     $elemMatch: {
       user: 'Mary Williams'
       }
    }
  }
)

Add Index

db.posts.createIndex({ title: 'text' })

Text Search

db.posts.find({
  $text: {
    $search: "\"Post O\""
    }
})

Greater & Less Than

db.posts.find({ views: { $gt: 2 } })
db.posts.find({ views: { $gte: 7 } })
db.posts.find({ views: { $lt: 7 } })
db.posts.find({ views: { $lte: 7 } })

Comparison Operators:

• $eq: Matches values that are equal to a specified value.

  { "age": { "$eq": 30 } }
  

• $gt: Matches values that are greater than a specified value.

  { "age": { "$gt": 30 } }
  

• $gte: Matches values that are greater than or equal to a specified value.

  { "age": { "$gte": 30 } }
  

• $lt: Matches values that are less than a specified value.

  { "age": { "$lt": 30 } }
  

• $lte: Matches values that are less than or equal to a specified value.

  { "age": { "$lte": 30 } }
  

• $ne: Matches all values that are not equal to a specified value.

  { "age": { "$ne": 30 } }
  

• $in: Matches any of the values specified in an array.

  { "age": { "$in": [30, 40] } }
  

• $nin: Matches none of the values specified in an array.

  { "age": { "$nin": [30, 40] } }
  

Logical Operators:

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

  { "$and": [{ "age": { "$gt": 20 } }, { "age": { "$lt": 40 } }] }
  

• $or: Joins query clauses with a logical OR and returns all documents that match the conditions of either clause.

  { "$or": [{ "age": { "$lt": 20 } }, { "age": { "$gt": 40 } }] }
  

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

  { "age": { "$not": { "$gt": 30 } } }
  

• $nor: Joins query clauses with a logical NOR and returns all documents that fail to match both clauses.

  { "$nor": [{ "age": { "$lt": 20 } }, { "age": { "$gt": 40 } }] }
  

Element Operators:

• $exists: Matches documents that have the specified field.

  { "age": { "$exists": true } }
  

• $type: Selects documents if a field is of the specified type.

  { "age": { "$type": "number" } }
  

Evaluation Operators:

• $expr: Allows the use of aggregation expressions within the query language.

  { "$expr": { "$gt": ["$qty", "$inStock"] } }
  

• $Schema: Validate documents against the given Schema.

  { "$Schema": { "required": ["name", "email"] } }
  

Array Operators:

• $all: Matches arrays that contain all elements specified in the query.

  { "tags": { "$all": ["mongodb", "database"] } }
  

• $elemMatch: Selects documents if the array field contains an element that matches all the specified query criteria.

  { "students": { "$elemMatch": { "name": "Alice", "grade": { "$gte": 80 } } } }
  

• $size: Selects documents if the array field is a specified size.

  { "comments": { "$size": 5 } }
  

Projection Operators:

• $: Projects the first element in an array that matches the query condition.

  { "scores": { "$elemMatch": { "$gt": 80 } } }
  

• $elemMatch: Projects the first element in an array that matches the specified condition.

  { "students": { "$elemMatch": { "grade": { "$gt": 90 } } } }
  

• $meta: Projects metadata such as the score of a document in a text search.

  { "score": { "$meta": "textScore" } }
  

Update Operators:

• $set: Sets the value of a field in a document.

  { "$set": { "status": "active" } }
  

• $unset: Removes the specified field from a document.

  { "$unset": { "status": "" } }
  

• $inc: Increments the value of a field in a document.

  { "$inc": { "quantity": 10 } }
  

• $mul: Multiplies the value of a field in a document.

  { "$mul": { "price": 1.1 } }
  

• $rename: Renames a field in a document.

  { "$rename": { "oldName": "newName" } }
  

• $min: Only updates the field if the specified value is less than the existing field value.

  { "$min": { "price": 100 } }
  

• $max: Only updates the field if the specified value is greater than the existing field value.

  { "$max": { "price": 200 } }
  

• $currentDate: Sets the value of a field to the current date or time.

  { "$currentDate": { "lastModified": true } }
  

Array Update Operators:

• $: Acts as a placeholder to update the first element that matches the query condition in an array.

  { "$[elem]": { "score": { "$gt": 80 } } }
  

• $[]: Updates all elements in an array.

  { "$[]": { "status": "done" } }
  

• $[<identifier>]: Acts as a placeholder to update all elements that match the arrayFilters condition in an array.

  { "$[elem]": { "score": { "$gt": 80 } } }