Turn array elements into separate pipeline rows.
Section: Core stages
Unwind an array
javascript
javascript
db.orders.aggregate([
{ $unwind: "$items" },
{ $group: { _id: "$items.sku", units: { $sum: "$items.qty" } } },
{ $sort: { units: -1 } }
])Explanation
`$unwind` is essential for analytics on nested arrays.
Learn the surrounding workflow
Compare similar commands or jump into common fixes when this command is part of a bigger troubleshooting path.
Related commands
Same sheet · prioritizing Core stages
Join with another collection
Use `$lookup` for collection-to-collection joins.
Run multiple result sets with $facet
Produce multiple related aggregations in one pipeline.
Count pipeline output
Return a final count after filters and transforms.