---
title: "Discussion on \"MongoDB Aggregation - II  [Class 3 ]\" | Hashnode"
description: "Discussion on \"MongoDB Aggregation - II  [Class 3 ]\". Relationships\nLearnings of this class\n\n$lookup Operator - use to get results from combining 2 or more collections\n\n$out Operator - to store the output in separate collection in that case $out is used.\n\n$project Operator -\n\n$count Operator - It will j..."
url: "https://hashnode.com/posts/mongodb-aggregation-ii-class-3/662df194ae0846429ccbaf74"
---

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# [MongoDB Aggregation - II \[Class 3 \]](https://suryathink.hashnode.dev/mongodb-aggregation-ii-class-3?utm_source=hashnode&utm_medium=feed)

Relationships Learnings of this class $lookup Operator - use to get results from combining 2 or more collections $out Operator - to store the output in separate collection in that case $out is used. $project Operator - $count Operator - It will j...

Apr 28, 2024 · 4 min read · suryathink.hashnode.dev  
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-   [#lookup](https://hashnode.com/tag/lookup)
-   [#mongodb-aggregation-pipeline](https://hashnode.com/tag/mongodb-aggregation-pipeline)
-   [#lookup-mongodb](https://hashnode.com/tag/lookup-mongodb)

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[Surya Prakash Singh](https://hashnode.com/@suryathink)

@suryathink · India

  
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