MongoDB Unique Index - Complete Tutorial

Create a Unique Index on Phone Number

Create a unique index on the phoneNumber field in the contacts collection and test inserting duplicate values.

Expected output: MongoDB rejects duplicate phoneNumber inserts with a duplicate key error.

Hint: Use createIndex() with unique: true and try inserting documents with the same phoneNumber.

Handle Duplicate Key Error in Application

Write code to catch and handle duplicate key errors when inserting documents with unique indexes.

Expected output: Your application gracefully handles duplicates without crashing.

Hint: Check for error code 11000 in your MongoDB driver error handling.

A unique index enforces uniqueness for the indexed field across documents, preventing duplicates. It is useful for maintaining data integrity and ensuring fields like emails or usernames are unique.

You create a unique index using the createIndex() method with the unique option set to true, for example: db.collection.createIndex({ field: 1 }, { unique: true }).

MongoDB throws a duplicate key error (code 11000) and rejects the insert or update operation.