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Mongo_CheatSheet

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Mongo Shell Cheat Sheet and Quickstart Guide.

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# MongoDB Shell Commands Cheat Sheet.

This is a Cheat Sheet for interacting with the Mongo Shell ( mongo on your command line). This is for MongoDB Community Edition.

Table Of Contents | CRUD
---|---
[Preface](#preface)| [Create](#create)|
[Docs](#docs)| [Read](#read)|
[Database](#databases)|[Update](#update)|
[Collections](#collections)| [Delete](#delete)|
[CRUD/Data](#data)| [Combos](#combos)|

## Preface:

1. After installing MongoDB and successfully running `mongod` to run the mongo service, open a new terminal window and type `mongo` to open a Mongo Shell.
2. You should see your command line change and be replaced with a `>` symbol. If you type `db` and see `test` or some other response then you have succesfully entered into the Mongo Shell and can start testing out the commands in this doc!

If you've never used the Mongo shell before, then I recommend skimming through these 3 doc as you read through this doc:

[Mongo Manual](https://docs.mongodb.com/manual/mongo/) can help you with getting started using the Shell.

[FAQ for MongoDB Fundamentals](https://docs.mongodb.com/manual/faq/fundamentals/) and other FAQs can be found in the side-bar after visiting that link.

The Mongo Shell reference can be found [here](https://docs.mongodb.com/manual/reference/method/).

## Quick Start
You can execute JavaScript commands in the shell. Type these commands into your commandline:
1. `use sampleDB` 
  - This makes a new database called sampleDB. It has no collections yet so it's not actually saved yet, which is why if you type `show dbs` it doesn't show up.
2. `db.cars.insert( [{make:"Honda", doors:2}, {make:"VW", doors:4}] )`
  - This makes a new collection called cars and inserts 2 documents into it. `.insert()` will make the collections if it doesn't already exist. Now that our db has a collection, if you type `show dbs` you will see it listed with the rest of the databases.
3. `db.cars.find({})`
  - This will list all the cars in your database.
  
This is where it gets fun:

1. `let tempCar = {make: "Ford", doors:3}`
2. `db.cars.insert(tempCar)`
3. ``` db.cars.find({}).forEach(car => print(`${car.make} has ${car.doors} doors.`))```

Notice that not only do we see out new Ford in our database, but we also get 3 messages printed out to the shell.

**Note:** Just because we can use JavaScript in the Shell doesn't mean we can use these same commands in Node.js though:

"JavaScript in MondgoDB: Although these methods use JavaScript, most interactions with MongoDB do not use JavaScript but use an idiomatic driver in the language of the interacting application."

This means that if we want to build an application then we should use the library provided by MongoDB. The [Node.js Docs](http://mongodb.github.io/node-mongodb-native/3.0/) are found here.

## Docs

Anything that looks like `db.<something>()` will be found in [Database Methods](https://docs.mongodb.com/manual/reference/method/js-database/).

Anything that looks like `db.collection.<something>` will be found in [Collection Methods](https://docs.mongodb.com/manual/reference/method/js-collection/).

Use `db.help()` to get a list of all database commands. ( Note that it's pretty long.)

Anything in `< >` should be replaced with your unique values. IE: You want to have a database called `Cars` you would use the command `use <db>` but you would type it as `use Cars`.

## Databases:

This table will list the commands most commonly used when working with the database as a whole.

Type| Command| Description
:--- |:--- | :---
Create/Connect | `use <db>` | Connects to a specific database. If none exists then one will automatically be created with that name. Note that it won't actually be saved until you add a collection to it! [Doc](https://docs.mongodb.com/manual/mongo/#working-with-the-mongo-shell)
List All | `show dbs` | Lists all Databases. Only DBs with collections will show up. [Doc](https://docs.mongodb.com/manual/mongo/#working-with-the-mongo-shell)
List Current| `db.getName()` | Lists the name of the currently selected databasse. [Doc](https://docs.mongodb.com/manual/reference/method/db.getName/#db.getName)
Return | `db` | Returns the currently selected Database. Allows you to use methods and chain commands. IE `db.createCollection('test')`. [Doc](https://docs.mongodb.com/manual/mongo/#working-with-the-mongo-shell)
Drop | `db.dropDatabase()` | Drops the currently selected Database. [Doc](https://docs.mongodb.com/manual/reference/method/db.dropDatabase/#db.dropDatabase)
Stats | `db.stats()` | Lists the stats about the current Database. [Doc](https://docs.mongodb.com/manual/reference/method/db.stats/#db.stats)

## Collections:

This Table lists the commands most commonly used when working with collections as a whole.

Type | Command | Description 
:--- | :--- | :---
Create | `db.createCollection('<collection>')` | Creates a new empty collection in the database. [Doc](https://docs.mongodb.com/manual/reference/method/db.createCollection/#db.createCollection)
List | `db.getCollectionNames()` | Lists all collections for a current Database. [Doc](https://docs.mongodb.com/manual/reference/method/db.getCollectionNames/#db.getCollectionNames)
Return | `db.getCollection('<collection>')` | Returns a collection. Can chain methods onto it. IE `db.getCollection.('authors').find({})`. [Doc](https://docs.mongodb.com/manual/reference/method/db.getCollection/)
Return/Create | `db.<collection>` | Similar to `db.getCollection()`, but if the collection doesn't exist, then the collection will be return, but not saved unless data is also added to that collection at the same time. IE: `db.items` does not add a collection to the database, but `db.items.insertOne({name: 'Mike'})` would, because data is also being added to the collection. Use `db.createCollection()` to add an empty collection. [Doc](https://docs.mongodb.com/manual/reference/method/js-collection/)
Drop | `db.<collection>.drop()` | Drops the collection from the database. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.drop/#db.collection.drop)
Rename | `db.<cllectn>.renameCollection('collection')` | Renames a collection. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.renameCollection/#db.collection.renameCollection)

## Data

This section is broken down into 5 sub-sections. The first 4 match the CRUD Verbs of Create, Read, Update, Delete, and the last one is a list of Combos like `findAndUpdate`. Check here for the [Mongo Docs on Crud](https://docs.mongodb.com/manual/crud/)

Couple notes here:

1. All of these commands start with `db.<collection>` where `<collection>` is the name of the collection you want to call these methods on. Any exceptions will be noted in the description.
2. `{query}` Is referring to queries like `{<field>: '<value>', <field>:'<value>', etc)`. IE: `{ book: 'Golden River Doth Flows', author: 'I.P. Freely', etc}`. They are field-value pairs that are used to make documents, and also used during searches, aka queries.

### Create

Type | Command | Description
:--- | :--- | :---
Create One | `.insertOne({<doc>})` | Inserts a document into the collection. IE: `db.cars.insertOne({make:"ford"})`. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.insertOne/#db.collection.insertOne)
Create One/Many | `.insert([{<doc>},{<doc>},{<doc>}] )` | Inserts One or more documents into the collection. If an array is passed in it will make a record of each document in the array. Otherwise it will accept a single document. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.insert/#db.collection.insert)

### Read

Most of these commands allow methods to be chained onto them.

Type | Command | Description 
:--- | :--- | :---
Count | `.count()` | Returns the number of items in the collection. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.count/#db.collection.count)
Return All | `.find({})` | Returns an array of all items in a collection. `.find()` Must be passed `{}` in order to return all documents. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.find/#db.collection.find)
Return All Filtered| `.find({query})` | Returns an array of items in a collection that match the query passed into `.find()`. See [Query and Project Operators](https://docs.mongodb.com/manual/reference/operator/query/) for extra info on querys. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.find/#db.collection.find)
Return One Filtered | `.findOne({query})` | Returns a document (not an array) of the first item found, filtering based off what was passed into `.findOne()`. Useful when searching by unique fields like `_id`, IE `db.cars.findOne({_id: 1})`. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.findOne/#db.collection.findOne)

### Update

Type | Command | Description 
:--- | :--- | :---
Update/Replace | `.update({query}, { $set: {query} }, options)` | The first argument is used as the query to find the document. The second argument specifies which field which to update. Exclude `$set:` and the entire document will be Replaced. Common options: `upsert: <boolean>` to keep it unique, and `multi: <boolean>` will update multiple documents if set to true. [Docs](https://docs.mongodb.com/manual/reference/method/db.collection.update/#db.collection.update) and [Field Operator Docs](https://docs.mongodb.com/manual/reference/operator/update-field/)
Update One/Many | `.updateOne()` and `.updateMany()`| Basically the same as the above function, except the `multi: <boolean>` option is basically defaulted to `false` and `true`, and isnt' an allowed option that can be passed in. [One Doc](https://docs.mongodb.com/manual/reference/method/db.collection.updateOne/#db.collection.updateOne), [Many Doc](https://docs.mongodb.com/manual/reference/method/db.collection.updateMany/#db.collection.updateMany)

### Delete

Type | Command | Description 
:--- | :--- | :---
Delete One | `.deleteOne({query})` | Deletes the first document that matches the query. Recommend to search by `_id` or another unique field. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.deleteOne/#db.collection.deleteOne)
Delete Many/All | `.deleteMany({query})` | Deletes all records that match the query. Leave the query blank to delete all documents. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.deleteMany/#db.collection.deleteMany)

### Combos

These are some combo commands that really just do the same thing as their base commands, but have a couple extra options.

All of these can leave their `{query}` blank and it will find the first document and execute it's verb on that item.

Command | Desctiption
:--- | :---
`.findOneAndDelete({query})` | Finds the first document that matches the query and deletes it. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndDelete/#db.collection.findOneAndDelete)
`.findOneAndUpdate({query}, {<update>}, {<options>})` | Finds the first document that matches the query in the first argument, and updates it using the second arguments. Has optional options as well. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndUpdate/#db.collection.findOneAndUpdate)
`.findOneAndReplace({query}, {<replacement>}, {<options>})` | Finds and replaces the document that matches the query. `<replacement>` cannot use update operators. [Doc](https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/#db.collection.findOneAndReplace)

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