MongoDB Primer

Source

When I have some to build sample sample toy PoC applications I tend to use MongoDB. I guess because it's schemaless, eats any JSON I give, has easy query language and good language support.

Concepts

Just like in MySQL I have a database which groups document collections together. Document collection is like a table in MySQL. It groups multiple logically related documents, e.g. people, items, payments, etc. Although, each document must not have the same fields. A document is simply JSON object. E.g. person document:

{
    "name": "Povilas",
    "age": 26,
    "gender": "male",
    "interests": ["systems", "books", "coding"]
}

Basic Commands

Show all databases:

> show dbs

Create a database:

> use my_db

This command won't create DB immediately. Once you insert the first document new database together with a table will be created.

Insert a document:

> db.table.insertOne({"name": "Povilas", "age", 26, "gender": "male"})

Delete document:

> db.table.deleteOne({"name": "Povilas"})

Show all documents:

> db.table.find()

Delete all documents:

> db.table.deleteMany({})

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