JavaScript 05: MongoDB

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Docs

https://www.mongodb.com/docs/

MongoDB Shell - https://www.mongodb.com/docs/mongodb-shell/

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Pending

Defining models in nodejs/react/nextjs

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MongoDb Concepts

Collections = Tables

Schema = maps to a Collection, uc: defines the shape of the documents within that collection.

Models = maps to a Schema, uc: creates+reads documents from MongoDB.

Document = Record

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Collection Namings

A collection name must always be lower-case and plural (with a 's').

Not doing so will create issues such as inability to connect with Mongoose.

https://stackoverflow.com/questions/10547118/why-does-mongoose-always-add-an-s-to-the-end-of-my-collection-name

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Collection vs Schema

Collection = Table

VS

Schema = Collection meta definition

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Schema vs Document

Schema = Collection meta definition

Document = records stored inside Collection

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Model

An instance of a model is called a document.

Tool to create and read documents from MongoDB.

Constructors compiled from Schema definitions.

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Model vs Collection

Collection = Table

VS

Model = Constructors compiled from Schema definitions, related to Collection via Schema

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Tools

Mongoose: create models to map objects to collections

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MongoDB Shell

Rename Collection / Table

db["oldCollectionILLEGALName"].renameCollection("someBetterName")

updateOne() vs updateMany() vs update()

update() deprecated since ~2018.

https://stackoverflow.com/questions/36719331/what-is-the-difference-between-update-and-updatemany-method-in-mongo-db

https://stackoverflow.com/questions/9038547/mongodb-update-every-document-on-one-field

Rename Field / Column

db["bottom-wealth-distros"].updateMany({}, { $rename: { "combined_wealth_gbp": "combined_wealth_billion_gbp" } } );

Add Field / Column

db["collectionname"].updateMany( {}, { $set: {"new_field": 1} } )

https://stackoverflow.com/questions/7714216/add-new-field-to-every-document-in-a-mongodb-collection

Divide Field Values By 1000

db["bottom-wealth-distros"].updateMany({}, {$mul: {"combined_wealth_gbp": 0.001}});

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Indexes

A database index makes queries faster by

Indexing is the way to get an unordered table into an order that will maximize the query’s efficiency while searching.