在mongodb中的聚合中合并多个组 [英] Combine multiple groups in an aggregation in mongodb

问题描述

如果我有这样的收藏夹:

If I have a collection like this:

{
    "store" : "XYZ",
    "total" : 100
},
{
    "store" : "XYZ",
    "total" : 200
},
{
    "store" : "ABC",
    "total" : 300
},
{
    "store" : "ABC",
    "total" : 400
}

我可以通过汇总获得集合中订单的$sum:

I can get the $sum of orders in the collection by aggregation:

db.invoices.aggregate([{$group: { _id: null, total: { $sum: "$total"}}}])

{
    "result": [{
            "_id": null,
            "total": 1000
        }
    ],
    "ok": 1
}

我可以得到按商店分组的订单的$sum:

And I can get the $sum of orders grouped by store:

db.invoices.aggregate([{$group: { _id: "$store", total: { $sum: "$total"}}}])

{
    "result": [{
            "_id": "ABC",
            "total": 700
        }, {
            "_id": "XYZ",
            "total": 300
        }
    ],
    "ok": 1
}

但是如何在一个查询中做到这一点?

But how can I do this in one query?

推荐答案

您可以如下汇总:

通过store字段

• $group，计算subtotal.

$project字段doc，可在下一个期间保持subtotal组的完整性 组.

$project a field doc to keep the subtotal group in tact, during the next group.

$group乘null并累积总净额.

代码:

db.invoices.aggregate([{
            $group: {
                "_id": "$store",
                "subtotal": {
                    $sum: "$total"
                }
            }
        }, {
            $project: {
                "doc": {
                    "_id": "$_id",
                    "total": "$subtotal"
                }
            }
        }, {
            $group: {
                "_id": null,
                "total": {
                    $sum: "$doc.total"
                },
                "result": {
                    $push: "$doc"
                }
            }
        }, {
            $project: {
                "result": 1,
                "_id": 0,
                "total": 1
            }
        }
    ])

输出:

{
    "total": 1000,
    "result": [{
            "_id": "ABC",
            "total": 700
        }, {
            "_id": "XYZ",
            "total": 300
        }
    ]
}

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