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What is aggregation in MongoDB?

MongoDBJunior~1 min read
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Aggregation in MongoDB is a mechanism for processing and transforming data within a collection to produce a final result: statistics, grouping, filtering, sorting, counts, and so on. It works through a pipeline, a sequence of stages, where each stage transforms or selects data before passing it on.

What this looks like

An example pipeline:

js
db.sales.aggregate([ { $match: { status: "A" } }, // filtering { $group: { _id: "$item", total: { $sum: "$price" } } } // grouping and totaling ])

What you can do with aggregation

  • filter, selecting only the documents you need ($match)
  • group, grouping and computing sums, averages, and so on ($group)
  • sort, sorting ($sort)
  • project, picking/changing fields ($project)
  • limit/skip, restricting the result set

When it's used

  • statistics (sums, averages, max/min)
  • reports
  • complex queries instead of several separate ones
  • preparing data for analytics

Summary

Aggregation is a powerful MongoDB tool for analytics and data processing through a pipeline of stages, letting you filter, group, and compute final values in a single query.

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