AliIybar: Created page with "Category:Node.js Category:MongoDb == Using References (Normalization) == Consistency let author = { name:'Ali' } let course = { author:'id' } === How i..."

2018-11-07T09:44:52Z

Created page with "Category:Node.js Category:MongoDb == Using References (Normalization) == Consistency let author = { name:'Ali' } let course = { author:'id' } === How i..."

New page

[[Category:Node.js]]
[[Category:MongoDb]]

== Using References (Normalization) ==
Consistency
let author = {
name:'Ali'
}

let course = {
author:'id'
}
=== How it's defined in model ===
const Course = mongoose.model('Course', new mongoose.Schema({
name:string
author:{
type:mongoose.Schema.Types.ObjectId,
ref:'Author'
}
}));
=== Querying data (Population) ===
async function listCourses(){
const courses = await Course
.find()
.populate('author')
.select('name author');
console.log(courses);
}

in order to include only some of the fields of populated data
.populate('author', 'name')
in order to exclude some of the fields of populated data
.populate('author', 'name -_id')

== Using Embedded Documents (Denormalization) ==
Performance
let course = {
author:{
name:'Ali'
}
}
[https://www.udemy.com/nodejs-master-class/learn/v4/t/lecture/9993130?start=0 https://www.udemy.com/nodejs-master-class/learn/v4/t/lecture/9993130?start=0]
=== How it's defined in model ===
By giving the schema name :
const Course = mongoose.model('Course', new mongoose.Schema({
name:string
author: authorSchema
}));
=== Creating ===
async function createCourse(name, author){
const course = new Course({
name,
author
});

createCourse('Node Course', new Author({ name:'Ali'}));
it saves as subdocuments and only updated by parent doc.

=== Update directly in DB ===
async function updateAuthor(courseId){
const course = await Course.update({ _id: courseId }, {
$set: {
'author.name:'John Smith'
}
});
}

updateAuthor('123123123');
== Hybrid ==
it's good for snapshot of data in a given point of time
let author = {
name : 'Ali'
// other properties
}

let course = {
author: {
id:'ref',
name:'Ali'
}
}
-----------------------
See Also : [[Mongo DB usage in Node]]

Mongo DB - Related Models - Revision history

AliIybar: Created page with "Category:Node.js Category:MongoDb == Using References (Normalization) == Consistency let author = { name:'Ali' } let course = { author:'id' } === How i..."