Mongodb Primary Key- Shikshaglobe

Content Creator: Satish kumar

What is Primary Key in MongoDB?

In MongoDB, _id field as the essential key for the assortment so that each report can be remarkably recognized in the assortment. The _id field contains an extraordinary ObjectID esteem.As a matter of course while embedding records in the assortment, in the event that you don't add a field name with the _id in the field name, then, at that point, MongoDB will consequently add an Object id field as displayed underneath

MongoDB Primary Key: Understanding and Implementing

In the world of databases, a primary key plays a vital role in ensuring data integrity and facilitating efficient data retrieval. MongoDB, a prominent NoSQL database, also employs primary keys to uniquely identify documents within a collection. In this guide, we'll delve into the concept of MongoDB primary keys, their significance, and how to effectively implement them.

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Table of Contents

  1. Introduction to MongoDB Primary Key
  2. Importance of Primary Keys
  3. Default _id Field as the Primary Key
  4. Custom Primary Keys
  5. Managing Primary Key Constraints
  6. Unique Index and Primary Key
  7. Conclusion
  8. Frequently Asked Questions (FAQs)

1. Introduction to MongoDB Primary Key

A primary key serves as a unique identifier for each record in a database table. It ensures that no two records have the same identifier, thus preventing duplicate entries and enabling efficient data retrieval. In MongoDB, primary keys are crucial for maintaining data consistency and supporting various database operations.

2. Importance of Primary Keys

Primary keys offer several key benefits:

  • Uniqueness: Every document within a collection has a unique primary key, ensuring no duplicate data.
  • Efficient Retrieval: Primary keys enable rapid retrieval of specific documents based on their unique identifiers.
  • Data Integrity: By preventing duplicates, primary keys uphold data integrity and accuracy.
  • Joins and Relationships: Primary keys play a role in establishing relationships between collections.

3. Default _id Field as the Primary Key

MongoDB assigns a default primary key to every document using the _id field. This field is automatically generated and assigned a unique value when a new document is inserted. The _id field can contain various data types, such as ObjectId, string, integer, etc.

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4. Custom Primary Keys

While the _id field is suitable for most scenarios, there are cases where you might want to use a custom primary key. This can be useful when you have a natural identifier for your data, such as a unique username or an email address.

To use a custom primary key, simply insert your documents with the desired primary key value. For example:

Javascript

db.users.insert({ _id: "john_doe", name: "John Doe", email: "john@example.com" });

5. Managing Primary Key Constraints

MongoDB does not provide explicit primary key constraints like relational databases do. However, the uniqueness of the primary key is enforced by the database system. If you attempt to insert a document with a duplicate primary key value, MongoDB will raise a duplicate key error.

6. Unique Index and Primary Key

Under the hood, MongoDB enforces primary key uniqueness using a unique index on the primary key field. This ensures that no two documents share the same primary key value. It's important to note that while primary keys are unique, they are not intended to be used as a means of ordering documents.

 Mongodb ObjectId()

At the point when you question the records in an assortment, you can see the ObjectId for each report in the assortment.If you have any desire to guarantee that MongoDB doesn't make the _id Field when the assortment is made and if you have any desire to determine your own id as the _id of the assortment, then, at that point, you want to expressly characterize this while making the assortment.While unequivocally making an id field, it should be made with _id in its name.We should take a gander at a model on how we can accomplish this.

Code Explanation:

We are expecting that we are making the principal record in the assortment and consequently in the above proclamation while making the assortment, we unequivocally characterize the field _id and characterize an incentive for it. Assuming that the order is executed effectively and presently utilize the track down order to show the records in the assortment, the accompanying Output will be shown

Mongodb ObjectId()

The result obviously shows that the _id field we characterized while making the assortment is currently utilized as the essential key for the assortment.


Must Know!

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