$[]

Azure Cosmos DB for MongoDB vCore 中的 $[] 运算符用于更新数组中与指定条件匹配的所有元素。 此运算符允许你对数组中的多个元素执行更新，而无需指定其位置。 当需要对数组中的所有项应用相同的更新时，它特别有用。

语法

db.collection.update(
   <query>,
   {
     $set: {
       <arrayField>.$[]: <value>
     }
   }
)

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：更新折扣百分比

此查询更新每个促销事件内的折扣数组中的所有元素。

db.stores.updateOne(
  { _id: "905d1939-e03a-413e-a9c4-221f74055aac" },
  {
    $inc: {
      "promotionEvents.$[].discounts.$[].discountPercentage": 5
    }
  }
)

示例 2：按类别更新销售额

此查询使用 $[] 运算符将所有类别的总销售额增加 10%。

db.stores.update(
  { _id: "905d1939-e03a-413e-a9c4-221f74055aac" },
  {
    $mul: {
      "sales.salesByCategory.$[].totalSales": 1.10
    }
  }
)

相关内容

• 查看有关 从 MongoDB 迁移到适用于 MongoDB 的 Azure Cosmos DB (vCore) 的选项。
• 详细了解 与 MongoDB 的功能兼容性。