mongoDB猫鼬组按月份和总金额

Question

我有这个orderdetails型号的

const model = new Schema(
{
district: { type: String },
category: String,
producer: String,
variety: String,
qty: String,
price: String,
subtotal: String,
},
{ timestamps: true }
);

我想在variety之前拿到月度销售报告。首先我过滤variety，然后按月份分组，计算出qty的总和

这是我的查询

const monthly = await OrderDetails.aggregate([
{
$match: {
variety,
},
},
{
$group: {
_id: {

month: { $month: "$createdAt" },
qty: { $sum: { $toInt: "$qty" } },
},
},
},
{ $sort: { _id: 1 } },
{
$project: {
qty: "$_id.qty",
Month: {
$arrayElemAt: [
[
"",
"Jan",
"Feb",
"Mar",
"Apr",
"May",
"Jun",
"Jul",
"Aug",
"Sep",
"Oct",
"Nov",
"Dec",
],
"$_id.month",
],
},
},
},
]);

但是输出是这样的

此查询的输出是此

[
{ _id: { month: 4, qty: 1 }, qty: 1, Month: 'Apr' },
{ _id: { month: 4, qty: 5 }, qty: 5, Month: 'Apr' }
]

但预期的输出是一个记录，总数量是6，就像这个

[
{ _id: { month: 4, qty: 6 }, qty: 6, Month: 'Apr' },

]

我的查询出了什么问题？

Answer 1

由于数量用于累加器，请从更改$group

{
$group: {
_id: {
month: { $month: "$createdAt" },
qty: { $sum: { $toInt: "$qty" } }
}
}
}

至

{
$group: {
_id: { month: { $month: "$createdAt" } },
qty: { $sum: { $toInt: "$qty" } }
}
}

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