$median (Median Accumulator)

Last updated: 2026-10-09

$median (Median Accumulator)

$median is an accumulator returning the median of a numeric field within a group, available since MongoDB 7.0. The median is the middle value when sorted and is robust to outliers. The method option picks approximate (faster) or exact (precise) computation.

📝 Syntax

{ $group: { _id: <key>, med: { $median: { input: "$field", method: "approximate" } } } }

Returns：Median value of the group

▶ Example

Run the commands below in your local mongosh (requires a running mongod):

// $median: median salary per department
db.salaries.aggregate([
  { $group: { _id: '$dept', med: { $median: { input: '$salary', method: 'approximate' } } } }
])

Output：

{ "_id": "ENG", "med": 42000 }

📌 Notes

• Requires MongoDB 7.0 or later
• method supports approximate and exact algorithms
• Missing fields are ignored; input should be numeric

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