$setDifference

De $setDifference operator retourneert een set die elementen bevat die in de ene set bestaan, maar niet in een andere set. Het behandelt matrices als sets en negeert dubbele waarden en elementvolgorde.

Syntaxis

{
  $setDifference: [ <array1>, <array2> ]
}

Parameterwaarden

Voorbeelden

Bekijk dit voorbeelddocument uit de winkelverzameling.

{
    "_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
                }
            ]
        }
    ]
}

Voorbeeld 1: Categorieën van te koop producten zoeken, maar niet met korting

Met deze query worden productcategorieën opgehaald die verkoopgegevens bevatten, maar geen kortingen.

db.stores.aggregate([
  { $match: {"_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74"} },
  {
    $project: {
      name: 1,
      soldCategories: "$sales.salesByCategory.categoryName",
      discountedCategories: {
        $reduce: {
          input: "$promotionEvents",
          initialValue: [],
          in: {
            $concatArrays: ["$$value", "$$this.discounts.categoryName"]
          }
        }
      }
    }
  },
  {
    $project: {
      name: 1,
      soldCategories: 1,
      discountedCategories: 1,
      categoriesWithoutDiscounts: {
        $setDifference: ["$soldCategories", "$discountedCategories"]
      }
    }
  }
])

Deze query retourneert het volgende resultaat.

[
  {
    "_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74",
    "name": "Proseware, Inc. | Home Entertainment Hub - East Linwoodbury",
    "soldCategories": [
      "Sound Bars",
      "Game Controllers",
      "Remote Controls",
      "VR Games"
    ],
    "discountedCategories": [
      "DVD Players",
      "Projector Lamps",
      "Media Players",
      "Blu-ray Players",
      "Home Theater Systems",
      "Televisions"
    ],
    "categoriesWithoutDiscounts": [
      "Sound Bars",
      "Home Theater Projectors",
      "Game Controllers",
      "Remote Controls",
      "VR Games"
    ]
  }
]

Voorbeeld 2: Distributietypen van medewerkers vergelijken

Met deze query wordt het verschil gevonden tussen twee lijsten met hypothetische personeelsvereisten.

db.stores.aggregate([
  { $match: {"_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74"} },
  {
    $project: {
      name: 1,
      requiredSkills: ["Sales", "Customer Service", "Technical Support", "Inventory Management"],
      availableSkills: ["Sales", "Customer Service", "Marketing", "Administration"],
      missingSkills: {
        $setDifference: [
          ["Sales", "Customer Service", "Technical Support", "Inventory Management"],
          ["Sales", "Customer Service", "Marketing", "Administration"]
        ]
      }
    }
  }
])

Deze query retourneert het volgende resultaat.

[
  {
    "_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74",
    "name": "Proseware, Inc. | Home Entertainment Hub - East Linwoodbury",
    "requiredSkills": [
      "Sales",
      "Customer Service", 
      "Technical Support",
      "Inventory Management"
    ],
    "availableSkills": [
      "Sales",
      "Customer Service",
      "Marketing",
      "Administration"
    ],
    "missingSkills": [
      "Technical Support",
      "Inventory Management"
    ]
  }
]