group mongodb aggregation code example
Example 1: mongodb aggregate group
#equivalent of the following SQL instruction:
# SELECT COUNT(*) FROM Table
# GROUP BY your_field
query = db.collection.aggregate([
{
"$group": {
"_id": "$your_field", #GROUP BY your_field
"total": {"$sum":1} #COUNT(*)
}
}
])
Example 2: group by mongo
db.sales.aggregate([
// First Stage
{
$match : { "date": { $gte: new ISODate("2014-01-01"), $lt: new ISODate("2015-01-01") } }
},
// Second Stage
{
$group : {
_id : { $dateToString: { format: "%Y-%m-%d", date: "$date" } },
totalSaleAmount: { $sum: { $multiply: [ "$price", "$quantity" ] } },
averageQuantity: { $avg: "$quantity" },
count: { $sum: 1 }
}
},
// Third Stage
{
$sort : { totalSaleAmount: -1 }
}
])