MongoDB Aggregation Pipeline Practice

Project Setup

Prerequisites

• Install MongoDB
• Install Node.js
• Install MongoDB Compass (optional, for GUI-based database management)

Installation Steps

1. Clone the repository:

   git clone <your-repo-url>
   cd mongodb-aggregation-practice

2. Install dependencies:

   npm install

3. Start MongoDB server (if not running):

   mongod --dbpath=/path/to/your/data

4. Run the script to insert sample data:

   node seed.js

5. Start practicing aggregation queries in practice.js.

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MongoDB Aggregation Pipeline Stages

Stage	Description
$match	Filters documents based on conditions (like WHERE in SQL).
$group	Groups documents by a field and performs aggregations (sum, count, etc.).
$project	Shapes documents by including/excluding fields.
$sort	Sorts the documents in ascending or descending order.
$limit	Limits the number of output documents.
$skip	Skips a specified number of documents.
$unwind	Deconstructs an array field into multiple documents.
$lookup	Performs a left join with another collection.
$addFields	Adds new fields to documents.
$set	Alias for $addFields (MongoDB 4.2+).
$replaceRoot	Replaces the document root with a specified field.
$facet	Performs multiple aggregation pipelines in a single query.
$bucket	Categorizes documents into groups based on a range.
$out	Writes the aggregation results to a new collection.
$merge	Merges results into an existing collection.
$count	Returns the count of documents processed in the pipeline.

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Running Aggregation Queries

Write and test your aggregation queries in practice.js. Example: