Group

The Group stage is used to group documents together and perform calculations across each group.

Examples

// Group by category and count items
Group([
    "_id": "$category",
    "count": ["$sum": 1]
])

// Group by multiple fields
Group([
    "_id": [
        "category": "$category",
        "supplier": "$supplier"
    ],
    "count": ["$sum": 1],
    "avgPrice": ["$avg": "$price"]
])

// Calculate statistics
Group([
    "_id": "$department",
    "totalSalary": ["$sum": "$salary"],
    "avgSalary": ["$avg": "$salary"],
    "minSalary": ["$min": "$salary"],
    "maxSalary": ["$max": "$salary"],
    "employeeCount": ["$sum": 1]
])

Common Aggregation Operators

• $sum: Calculates sum

• $avg: Calculates average

• $min: Finds minimum value

• $max: Finds maximum value

• $first: First value in group

• $last: Last value in group

• $push: Creates an array of values