What is Database?

• Software designed to efficiently store and retrieve data is called a Database Management System (DBMS).

• The server computer where the DBMS is installed can be referred to as the Database Server (DB Server).

• When people commonly say "data is stored in a database," they are referring to the fact that the data is managed by the DBMS on the DB Server.

Two types of DB

• Relational Database (RDB): A type of database that focuses on maintaining data with defined formats and relationships among data to ensure consistency and integrity of data is called a relational database.

  • Consistency and integrity of data: data with high integrity and consistency.

• Non-relational Database (NoSQL): Any type of database that does not belong to the relational database category is referred to as a non-relational database or NoSQL database. Non-relational databases are flexible in terms of data format and can be scaled easily, but if data is not properly managed, the data stored in the database may become unreliable.

  • This type of database is often adopted by many startups for its flexibility in design.

What is MongoDB?

• One of the most popular NoSQL databases used by many developers domestically and internationally.

• All data is stored in JSON format.

• It has the advantage of easily storing complex structures.

• It is available for free to use.

• It can easily scale up or down.

Relationship between Web Server and DB Server

• The web server provides the data and functionalities requested by the web client.

• The DB server stores data for optimal performance and provides the data requested by the DB client.

• Ultimately, the two servers differ only in what they provide, but their basic principles are similar.

MongoDB

MongoDB Client - Studio 3T

• Studio 3T is a MongoDB client designed to assist with using MongoDB, similar to an API client that helps with API usage.

• Studio 3T is a program that provides an easy-to-use GUI for managing data stored in MongoDB, displaying it in a user-friendly manner.

CRUD Command in MongoDB

1. find: db.collectionName.find({})

2. insert one: db.collectionName.insertOne({ key: "value", key2: "값" })

3. delete one: db.collectionName.deleteOne({ _id: ObjectId("...")})

4. update one: db.collectionName.updateOne({ _id: ObjectId("...")}, {$set : {attribute}})

Mongoose

Document in mongoose

• A document in mongoose refers to each individual piece of data that is stored in MongoDB.

• It consists of one or more key-value pairs, in JSON format.

{
    "_id": ObjectId("6682192a1c155bd2f27881"),
    "name": "lyw",
}

Collection in mongoose

• A collection in mongoose is similar to a table in relational databases and can hold multiple documents in JSON format.

Schema in mongoose

• A schema in mongoose defines what type of values can be included in the documents of a collection.

• It is used for modeling data and specifies the structure of the data.

• ❓ Some common types in a schema are:

  • null: for null values or non-existent fields

    • ex: null

  • String: for strings

    • ex: "mongoDB"

  • Number: for numbers

    • ex: 3.14

  • Date: for dates

    • ex: new Date()

  • Buffer: for buffers that can hold files or non-UTF-8 encoded strings

    • ex: 0x65

  • Boolean: for true or false

    • ex: true

  • ObjectId(Schema.Types.ObjectId): for object IDs, often used for referencing other objects

    • ex: ObjectId()

  • Array: for arrays of values

    • ex: ["a", "b", "c"]

Model in mongoose

• A model in mongoose is responsible for defining the structure of data that will be stored in the database.

• It is created using a schema and provides functions to perform operations on MongoDB.

• It is used to create documents when storing data.