$reverseArray

運算子 $reverseArray 是用來反轉數位中項目的順序。 當您需要以相反順序處理或顯示數位元素時，這個運算符會很有用。 它是數位表達式運算元，可在匯總管線內使用。

語法

{
  $reverseArray: <array>
}

參數

參數	Description
<array>	您想要反轉的陣列。

範例

請參考商店集合中的此範例檔。

{
    "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
    "name": "Lakeshore Retail | DJ Equipment Stop - Port Cecile",
    "location": {
        "lat": 60.1441,
        "lon": -141.5012
    },
    "staff": {
        "totalStaff": {
            "fullTime": 2,
            "partTime": 0
        }
    },
    "sales": {
        "salesByCategory": [
            {
                "categoryName": "DJ Headphones",
                "totalSales": 35921
            }
        ],
        "fullSales": 3700
    },
    "promotionEvents": [
        {
            "eventName": "Bargain Blitz Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 3,
                    "Day": 11
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 2,
                    "Day": 18
                }
            },
            "discounts": [
                {
                    "categoryName": "DJ Turntables",
                    "discountPercentage": 18
                },
                {
                    "categoryName": "DJ Mixers",
                    "discountPercentage": 15
                }
            ]
        },
        {
            "eventName": "Discount Delight Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 5,
                    "Day": 11
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 5,
                    "Day": 18
                }
            }
        }
    ],
    "tag": [
        "#ShopLocal",
        "#FashionStore",
        "#SeasonalSale",
        "#FreeShipping",
        "#MembershipDeals"
    ]
}

範例 1：反轉陣列的順序

此查詢示範運算子在陣列順序 promotionEvents 上執行反轉的使用方式。

db.stores.aggregate([
    //filtering to one document
    {
        $match: {
            _id: "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5"
        }
    },
    {
        $project: {
            _id: 1,
            name: 1,
            promotionEventsReversed: {
                $reverseArray: "$promotionEvents"
            }
        }
    },
    // Include only _id, name, promotionalDates and eventName fields in the output 
    {
        $project: {
            _id: 1,
            name: 1,
            "promotionEventsReversed.promotionalDates": 1,
            "promotionEventsReversed.eventName": 1
        }
    }
])

此查詢會傳回下列結果。

[
    {
        "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
        "name": "Lakeshore Retail | DJ Equipment Stop - Port Cecile",
        "promotionEventsReversed": [
            {
                "eventName": "Discount Delight Days",
                "promotionalDates": {
                    "startDate": {
                        "Year": 2024,
                        "Month": 5,
                        "Day": 11
                    },
                    "endDate": {
                        "Year": 2024,
                        "Month": 5,
                        "Day": 18
                    }
                }
            },
            {
                "eventName": "Bargain Blitz Days",
                "promotionalDates": {
                    "startDate": {
                        "Year": 2024,
                        "Month": 3,
                        "Day": 11
                    },
                    "endDate": {
                        "Year": 2024,
                        "Month": 2,
                        "Day": 18
                    }
                }
            }
        ]
    }
]

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• 檢視從 MongoDB 遷移到 Azure DocumentDB 的選項。
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