$rank

该 $rank 运算符将排名分配给数据集分区中的每个文档。 排名是根据指定的排序顺序确定的。

Syntax

{
    $setWindowFields: {
        partitionBy: < expression > ,
        sortBy: {
            < field >: < order >
        },
        output: {
            < outputField >: {
                $rank: {}
            }
        }
    }
}

参数

例子

请考虑商店集合中的这个示例文档。

{
    "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
    "name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
    "location": {
        "lat": -89.2384,
        "lon": -46.4012
    },
    "staff": {
        "totalStaff": {
            "fullTime": 8,
            "partTime": 20
        }
    },
    "sales": {
        "totalSales": 75670,
        "salesByCategory": [
            {
                "categoryName": "Wine Accessories",
                "totalSales": 34440
            },
            {
                "categoryName": "Bitters",
                "totalSales": 39496
            },
            {
                "categoryName": "Rum",
                "totalSales": 1734
            }
        ]
    },
    "promotionEvents": [
        {
            "eventName": "Unbeatable Bargain Bash",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 6,
                    "Day": 23
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 7,
                    "Day": 2
                }
            },
            "discounts": [
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 7
                },
                {
                    "categoryName": "Bitters",
                    "discountPercentage": 15
                },
                {
                    "categoryName": "Brandy",
                    "discountPercentage": 8
                },
                {
                    "categoryName": "Sports Drinks",
                    "discountPercentage": 22
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 19
                }
            ]
        },
        {
            "eventName": "Steal of a Deal Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 21
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 29
                }
            },
            "discounts": [
                {
                    "categoryName": "Organic Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "White Wine",
                    "discountPercentage": 20
                },
                {
                    "categoryName": "Sparkling Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 17
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 23
                }
            ]
        }
    ]
}

示例 1：按销售量对商店进行排名

若要按销售量对“第一向上顾问”公司中的所有商店进行排名，请首先运行查询来对公司内的商店进行分区。 然后，按销售量升序对生成的商店进行排序，并使用$rank运算符对结果集中的已排序文档进行排名。

db.stores.aggregate([{
    "$match": {
        "company": {
            "$in": ["First Up Consultants"]
        }
    }
}, {
    "$setWindowFields": {
        "partitionBy": "$company",
        "sortBy": {
            "sales.totalSales": -1
        },
        "output": {
            "rankBySales": {
                "$rank": {}
            }
        }
    }
}, {
    "$project": {
        "company": 1,
        "name": 1,
        "rankBySales": 1
    }
}])

此查询返回的前三个结果为：

[
    {
        "_id": "a0386810-b6f8-4b05-9d60-e536fb2b0026",
        "name": "First Up Consultants | Electronics Stop - South Thelma",
        "company": "First Up Consultants",
        "rankBySales": 1
    },
    {
        "_id": "ad8af64a-d5bb-4162-9bb6-e5104126566d",
        "name": "First Up Consultants | Electronics Emporium - South Carmenview",
        "company": "First Up Consultants",
        "rankBySales": 2
    },
    {
        "_id": "39acb3aa-f350-41cb-9279-9e34c004415a",
        "name": "First Up Consultants | Bed and Bath Pantry - Port Antone",
        "company": "First Up Consultants",
        "rankBySales": 3
    }
]

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