Designing one-to-many mapping in mongoDB

In one-to-many relationship one entity maps to many entities.

Example

company – employees

city – people

post - comments

One company has many employees. Many people live in one city. One post can have many comments.

There are two ways to model one-to-many mapping.

1.   Embed documents

2.   Separate documents

Embed documents

You can embed all employees inside company.

{
        "_id" : 1,
        "company_name" : "ABC",
        "employees" : [
                {
                        "id" : 1,
                        "name" : "Hari Krishna"
                },
                {
                        "id" : 2,
                        "name" : "Dhrona"
                }
        ]
}

Separate Documents

You can create one collection for company and another collection for employees and refer company id in employee collection.

Company collection

{ "_id" : 1, "company_name" : "ABC" }

Employee collection

{ "_id" : 1, "company_Id" : 1, "name" : "Hari Krishna" }

{ "_id" : 2, "company_Id" : 1, "name" : "Dhrona" }

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