$dateAdd

该 $dateAdd 运算符将指定的时间单位数添加到日期。 在需要基于给定日期和时间间隔计算未来日期的情况下，它非常有用。

Syntax

$dateAdd: {
   startDate: <expression>,
   unit: <string>,
   amount: <number>,
   timezone: <string>  // Optional
}

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：向日期添加天数

此查询通过将 eventName 7 天添加到从嵌套年份、月和日字段构造的日期来计算 newEndDate 。 结果是一个简化的文档，其中显示了事件名称和其扩展结束日期。

db.stores.aggregate([
  { $match: { _id: "e6410bb3-843d-4fa6-8c70-7472925f6d0a" } },
  { $unwind: "$promotionEvents" },
  { $unwind: "$promotionEvents.promotionalDates" },
  {
    $project: {
      eventName: 1,
      newEndDate: {
        $dateAdd: {
          startDate: {
            $dateFromParts: {
              year: "$promotionEvents.promotionalDates.endDate.Year",
              month: "$promotionEvents.promotionalDates.endDate.Month",
              day: "$promotionEvents.promotionalDates.endDate.Day"
            }
          },
          unit: "day",
          amount: 7
        }
      }
    }
  }
])

此查询返回以下结果。

[
   {
     "_id": "e6410bb3-843d-4fa6-8c70-7472925f6d0a",
     "newEndDate": "2024-10-06T00:00:00.000Z"
   }
]

示例 2：将月份添加到日期

此聚合查询通过从嵌套升级字段将 1 个月添加到重新构造的开始日期来投影 eventName 并计算 newStartDate。 它有助于根据原始计划确定调整的事件开始日期。 此查询从嵌套升级事件数据返回每个文档的 eventName 和 1 个月后的 newStartDate。

db.stores.aggregate([
  { $match: { _id: "e6410bb3-843d-4fa6-8c70-7472925f6d0a" } },
  { $unwind: "$promotionEvents" },
  { $unwind: "$promotionEvents.promotionalDates" },
  {
    $project: {
      eventName: "$promotionEvents.eventName",
      newStartDate: {
        $dateAdd: {
          startDate: {
            $dateFromParts: {
              year: "$promotionEvents.promotionalDates.startDate.Year",
              month: "$promotionEvents.promotionalDates.startDate.Month",
              day: "$promotionEvents.promotionalDates.startDate.Day"
            }
          },
          unit: "month",
          amount: 1
        }
      }
    }
  }
])

此查询返回以下结果。

[
   {
     "_id": "e6410bb3-843d-4fa6-8c70-7472925f6d0a",
     "eventName": "Massive Markdown Mania",
     "newStartDate": "2024-10-21T00:00:00.000Z"
   }
]

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