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$toDecimal

适用对象： MongoDB vCore

运算符 $toDecimal 将表达式转换为十进制值。 Long、Double 或 Int 值只是转换为十进制数据类型，而十进制值按原样返回。 值为 true 的布尔值返回为 1，而 false 则返回为 0。 最后，ISODate 作为 Decimal 值返回，该值对应于自 1970 年 1 月 1 日以来的毫秒数（由 ISODate 值表示）。

语法

运算符的 $toDecimal 语法为：

{ "$toDecimal": <expression> }

参数

参数 DESCRIPTION
expression 要转换为十进制值的指定值

例子

请查看 StoreData 数据库中 stores 集合的这个示例文档。

{
    "_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：将 Double 值转换为十进制值

db.stores.aggregate([
{
    "$match": {
        "_id": "b0107631-9370-4acd-aafa-8ac3511e623d"
    }
},
{
    "$project": {
        "originalLatitude": "$location.lat",
        "latitudeAsDecimal": {
            "$toDecimal": "$location.lat"
        }
    }
}])

此查询返回以下结果：

{
    "_id": "b0107631-9370-4acd-aafa-8ac3511e623d",
    "originalLatitude": 72.8377,
    "latitudeAsDecimal": "Decimal128('72.8377000000000')"
}

示例 2：将 ISODate 值转换为十进制值

db.stores.aggregate([
{
    "$match": {
        "_id": "b0107631-9370-4acd-aafa-8ac3511e623d"
    }
},
{
    "$project": {
        "dateAsDecimal": {
            "$toDecimal": ISODate("2025-01-06T00:00:00.000Z")
        }
    }
}])

此查询返回以下结果：

{
    "_id": "b0107631-9370-4acd-aafa-8ac3511e623d",
    "dateAsDecimal": "Decimal128('1736121600000')"
}

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