sahilrajput.com

Readme

Quick Links:

Learn mongo and mongoosejs - Github Repository: Click here

Some used mongodb operators

Other Sources

Traversy Media: @gist, Video @youtube.
Tutorials Point: Tutorials point - Mongodb.
Online mongodb-cli Playground: Click here - mongoplayground.net, Click here 2
Detect a file type restred db file: Click here

Exploring data with official mongodb extension with mogno playground in vscode

Docs: Click here

FYI: Using my own way of creatinig files and running them on save with nodemon is much much better though.

Using mongoexport, mongorestore, etc

Which one is the preferred choice Mongodump VS Mongoexport for upgrading mongoDB database?: Click here
Google Search: Click here

Search using regex in db

FYI: Its good to do indexing if you have large number of records for efficient searching.

FYI: In below query you could have used / to write concise queries (but online playground doesn’t allow that syntax yet):

Learn all about regext here in docs.

LEARN: i option helps to do a case-insensitive search

db.collection.find({
  name: {
    "$regex": /hil/i
  }
})

Roll

Note (for Windows User) : git-bash isn’t performing good with mongo shell environment, so prefer cmd for now.

# To open a mongo shell environment.
mongo
# TIP: To clear logs in `mongo` shell, use ctrl+L hotkey or use command -> cls


#close mongo shell
Ctrl+c # or use`exit` command 


#show all dbs
show dbs


#to select db (or create **new db** if doesn't exist)
use test1


#shows currently selected db name
db


#Show the collections of currently selected db.
show collections


#creates new collection 'posts' in currently selected db.
db.createCollection('posts')


#Drop a collection named `mycollection`
use myDb # Select a database
db.mycollection.drop() # Drop collection.


# Dropping a db:
use myDb # Select a database
db.dropDatabase() # Drop selected database.


# Insert a post
db.posts.insert({
	title: 'Post One',
	body: 'Body of post one',
	category: 'News',
	likes: 4,
	tags: ['news', 'events'],
	user: {
	name: 'John Doe',
	status: 'author'
	},
	data: Date()
})


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


# Find posts
db.posts.find()
db.posts.find().pretty()


# Find posts with some filter
db.posts.find({category: 'News'})
db.posts.find({category: 'News'}).pretty()


# Find posts and sort
db.posts.find().sort({title:1}).pretty()
#title: 1 means sort by title in ascending order.


# Find posts and sort in descending order
db.posts.find().sort({title:-1}).pretty()
#title: -1 means sort by title in descending order.


#show first two posts only.
db.posts.find().limit(2)


#show only first two posts in descending ordered list by title property.
db.posts.find().sort({title: -1}).limit(2)


#amazing!!, Print documents in a particular required format
db.posts.find().forEach(function(doc) { print('Blog Post: ' + doc.title)})


#shows only the first found document.
db.posts.findOne({category: 'News'})

Case 1 - `update()` method

db.posts.find({title: 'Post Random'})

db.posts.update(
	{ title: 'Post Random' },
	{
		title: 'Post Two',
		body: 'New Post 2 body',
		date: Date()
	}
)

db.posts.find({title: 'Post Two'})

Case 2 - `update()` method with `upsert: true`

tldr:

update() method in Case 1 doesn’t create a new document if the searched document doesn’t exists.

upsert: true in update() method creates a completely new document if the matching document is not found.

# Reset our posts collection
db.posts.deleteMany({})

db.posts.insertMany([
{
	title: 'Post Two',
	body: 'Body of post two',
	category: 'Technology',
	data: Date()
},
{
	title: 'Post Two',
	body: 'Body of post two - DUPLICATE',
	category: 'Technology - DUPLICATE',
	data: Date()
},
{
	title: 'Post Two - a',
	body: 'Body of post three',
	category: 'News',
	data: Date()
}
])


db.posts.find({title: 'Post Two'})
# Obeservation 1: Shows only the exact two posts that matches i.e., first two posts in the above three posts we added.

db.posts.update(
	{ title: 'Post Two' },
	{
		title: 'Post Two',
		body: 'New Post 2 body',
		date: Date()
	},
	{ upsert: true}
)
# Output: WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
# Observation 2: Only the first post(since nModified is 1 that means a single document) that matched the filter is only updated out of two matched!


db.posts.find({title: 'Post Two'})
# Observaion 2: VERIFIED

###IMPORTANT:
# Previous document's data will be OVERWRITTEN.
# The second object is **OPTIONAL**. The second options object in current example tells that if the record doesn't exist then, create it. (upsert name comes from like UPdate OR insERT )
##Watch for next example for CLARIFICATION.


# ___ Debugging commands

# Get all posts
db.posts.find()

Case 3 - `update()` method

tldr: Add content to document.

db.posts.find({title: 'Post Two'}).pretty()

# So this will update a document keeping all the earlier content as it is.
db.posts.update(
	{ title: 'Post Two' },
	{
		$set: {
				body: 'Body of post 2',
				category: 'Techonology',
			  }
	}
)

db.posts.find({title: 'Post Two'}).pretty()

Case 4 - `$inc` operator with `update()` method

tldr: The first matching document’s likes property will be incremented by 2(if the property doesn’t exists then the property will be set to 2).

# Reset our posts collection
db.posts.deleteMany({})

db.posts.insertMany([
{
	title: 'Post One',
	body: 'Body of post One',
	category: 'Technology',
	data: Date()
},
{
	title: 'Post One',
	body: 'Body of post One - DUPLICATE',
	category: 'Technology - DUPLICATE',
	data: Date()
},
{
	title: 'Post One - a',
	body: 'Body of post One - DUPLICATE - DUPLICATE',
	category: 'News',
	data: Date()
}
])

db.posts.find({title: 'Post One'}).pretty()

db.posts.update(
{title: 'Post One'},
{
	$inc: { likes: 2}
})
# Output: WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
# Observation1 : 1 document updated.

db.posts.find({title: 'Post One'}).pretty()
#Observation2 : The very first post is updated with property `likes: 2`.
#Observattion3 : Re-running the last update command will make the property to `likes: 4`

Case 5 - `update()` method

# Reset our posts collection
db.posts.deleteMany({})

db.posts.insertMany([
{
	title: 'Post One',
	likes: 10
},
{
	title: 'Post One',
	likes: 10
},
{
	title: 'Post One - a',
	likes: 10
}
])

db.posts.find({title: 'Post One'}).pretty()
#Observation1: Finds first two document which we added using above command.

db.posts.update(
	{title: 'Post One'},
	{
		$rename: { likes: 'views'}
	}
)
# Output: WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
# Observation2: 1 Document updated.

db.posts.find({title: 'Post One'}).pretty()
# PROVES (Observation2): Only the first matched document's property name i.e., `likes` updated to `views`.

`remove()` method

# Reset our posts collection
db.posts.deleteMany({})

db.posts.insertMany([
{
	title: 'Post One',
	likes: 10
},
{
	title: 'Post One',
	likes: 10
},
{
	title: 'Post One - a',
	likes: 10
}
])

db.posts.find({title: 'Post One'}).pretty()
#Observation1: Finds first two document which we added using above command.

db.posts.remove({title: 'Post One'})
# Output: WriteResult({ "nRemoved" : 2 })
# Observation: Two documents updated.

`$set` operator ( subdocuments )

# Reset our posts collection
db.posts.deleteMany({})

db.posts.insertMany([
{
	title: 'Post One',
	likes: 10
},
{
	title: 'Post One',
	likes: 10
},
{
	title: 'Post One - a',
	likes: 10
}
])

db.posts.find({title: 'Post One'}).pretty()
#Observation0: Finds first two document which we added using above command.

db.posts.update(
	{ 	title: 'Post One' },
	{ 	$set:	{
					comments:	[
									{
										user: 'Mary Williams',
										body: 'Comment One',
										date: Date()
									},
									{
										user: 'Harry White',
										body: 'Comment Two',
										date: Date()
									}
								]
				}
	}
)
# Observation1: The first matching document is now has new comment property as added.

db.posts.find({title: 'Post One'}).pretty()
# Below ouput PROVES Observation1
# Output: 
# {
#         "_id" : ObjectId("624de10adfa76c8c1b1fdf35"),
#         "title" : "Post One",
#         "likes" : 10,
#         "comments" : [
#                 {
#                         "user" : "Mary Williams",
#                         "body" : "Comment One",
#                         "date" : "Thu Apr 07 2022 00:20:53 GMT+0530 (IST)"
#                 },
#                 {
#                         "user" : "Harry White",
#                         "body" : "Comment Two",
#                         "date" : "Thu Apr 07 2022 00:20:53 GMT+0530 (IST)"
#                 }
#         ]
# }
# {
#         "_id" : ObjectId("624de10adfa76c8c1b1fdf36"),
#         "title" : "Post One",
#         "likes" : 10
# }
# 

`$elemMatch` operator

tldr: $elemMatch finds a document by searching for the filter against each array element as specified in the search query.

# Reset our posts collection
db.posts.deleteMany({})

db.posts.insertMany([
	{
			"title" : "Post One",
			"likes" : 10,
			"comments" : [
					{
							"user" : "Mary Williams",
							"body" : "Comment One",
							"date" : "Thu Apr 07 2022 00:20:53 GMT+0530 (IST)"
					},
					{
							"user" : "Harry White",
							"body" : "Comment Two",
							"date" : "Thu Apr 07 2022 00:20:53 GMT+0530 (IST)"
					}
			]
	}
])


db.posts.find({ comments: 	{ $elemMatch: {user: 'Mary Williams'}}	}).pretty()
# Output:
# {
#         "_id" : ObjectId("624de303dfa76c8c1b1fdf38"),
#         "title" : "Post One",
#         "likes" : 10,
#         "comments" : [
#                 {
#                         "user" : "Mary Williams",
#                         "body" : "Comment One",
#                         "date" : "Thu Apr 07 2022 00:20:53 GMT+0530 (IST)"
#                 },
#                 {
#                         "user" : "Harry White",
#                         "body" : "Comment Two",
#                         "date" : "Thu Apr 07 2022 00:20:53 GMT+0530 (IST)"
#                 }
#         ]
# }

-»» TODO: clean below notes

`createIndex()` method

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

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

#Above serach will match two posts i.e, Post Two and Post Three.

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

#Above search will match one posts i.e, Post One.

`$set` operator

db.posts.find({title: 'Post Two'}).pretty()

db.posts.update({title: 'Post Two'}, {$set: { views: 10}})

db.posts.find({title: 'Post Two'}).pretty()

db.posts.find(
{
	views: {
		$gt: 8
	}
}).pretty()

#above will search for documents having their `views` property having value more than 8. This would return multiple documents if there are such matching documents.

`$gte` operator

db.posts.find(
{
	views: {
		$gte: 8
	}
}).pretty()

#above will search for documents having their `views` property having value more than or EQUAL TO 9. This would return multiple documents if there are such matching documents.

Source of this video content: https://www.youtube.com/watch?v=-56x56UppqQ&t=867s

Amazing “Traversy Media - MongoDB Crash Course”.

inspiration 1 - fullstackopen.com/en

db.posts.insert({
	title: 'Post Five',
	fruits: ["mango","apple","banana"]
})

db.posts.find({title: 'Post Five'}).pretty()

db.posts.find(
{
  fruits: {
    $in: ["mango"]
  } 
}).pretty()

#So, thats how $in operator works.

inspiration 2 - fullstackopen.com/en

db.posts.insert({
	title: 'Post Five',
	fruits: ["mango","apple","banana"]
})

db.posts.insert({
	title: 'Post Six',
	fruits: ""
})

db.posts.find({title: 'Post Five'}).pretty()
db.posts.find({title: 'Post Six'}).pretty()

db.posts.find(
{
  fruits: {
    $exists: false
  } 
}).pretty()

#above will return all documents that has does not has fruits property for it.

db.posts.find(
{
  fruits: {
    $exists: true
  } 
}).pretty()

#above will return all documents that has fruits property for it
##Note this will also return document with title "Post Six" @line7 too, as it has fruits property too.

sahilrajput.com

Readme

Exploring data with official mongodb extension with mogno playground in vscode

Using mongoexport, mongorestore, etc

Search using regex in db

Roll

Case 1 - update() method

Case 2 - update() method with upsert: true

Case 3 - update() method

Case 4 - $inc operator with update() method

Case 5 - update() method

remove() method

$set operator ( subdocuments )

$elemMatch operator

createIndex() method

$set operator

$gte operator