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 Row

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 Rows

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 Rows

db.posts.find()

Get All Rows Formatted

db.posts.find().pretty()

Find Rows

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

Sort Rows

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

Count Rows

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

Limit Rows

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 Row

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

Find Specific Fields

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

Update Row

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 Row

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 } })

Adding update/delete examples using updateOne, updateMany, deleteOne, deleteMany with $set, and $unset.

1) UPDATE

• updateOne() modifies only the first matching document.
• updateMany() modifies all matching documents.
• $set: Updates (or adds) the specified fields.
• $unset: Removes the specified fields.

Update One:
db.posts.updateOne( { title: "Post One" }, { $set: { body: "Updated body for Post One" }, $unset: { category: "" } } );
Update Many:
db.posts.updateMany( { category: "News" }, { $set: { category: "Updated News" } } );

2) DELETE

• deleteOne() removes only the first matching document.
• deleteMany() removes all matching documents.

Delete One:
db.posts.deleteOne( { title: "Post Four" } );
Delete Many
db.posts.deleteMany( { category: "Entertainment" } );

1) Comparison operator examples:

$ne (Not equals) - Find documents where 'category' is NOT 'News':
db.posts.find({ category: { $ne: "News" } });

$in (Matches Any Of) - Find documents where 'category' is either 'News' OR 'Technology':
db.posts.find({ category: { $in: ["News", "Technology"] } });

$nin (Not In) - Find documents where 'category' is neither 'News' nor 'Technology':
db.posts.find({ category: { $nin: ["News", "Technology"] } });

2) Logical operator examples:

$and (Matches All) - Find documents where 'category' is "News" AND 'user.name' is "John Doe":
db.posts.find({ $and: [ { category: "News" }, { "user.name": "John Doe" } ] });

$nor (Matches None) - Find documents where 'category' is neither "News" NOR "Technology":
db.posts.find({ $nor: [ { category: "News" }, { category: "Technology" } ] });

$or (Matches Any) - Find documents where 'category' is "News" OR "Technology":
db.posts.find({ $or: [ { category: "News" }, { category: "Technology" } ] });

$not (With $lte & $regex) - Find documents where 'views' is NOT less than or equal to 100 (i.e., greater than 100), and the 'title' does not start with "Post":
db.posts.find({ $and: [ { views: { $not: { $lte: 100 } } }, { title: { $not: /^Post/ } } ] });

Thank You