$or

The $or operator performs a logical OR operation on an array of expressions and retrieves documents that satisfy at least one of the specified conditions.

Syntax

{
    $or: [{
        < expression1 >
    }, {
        < expression2 >
    }, ..., {
        < expressionN >
    }]
}

Parameters

Parameter Description
expression An array of expressions, where at least one must be true for a document to be included

Examples

Let's understand the usage with sample json from stores dataset.

{
    "_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
                }
            ]
        }
    ]
}

Example 1: Use OR operation as logical-query

The example helps to find stores with more than 15 full-time staff or more than 20 part-time staff, run a query using the $or operator on both the conditions. Then, project only the name and staff fields from the stores in the result set.

db.stores.find(
  {
    $or: [
      { "staff.employeeCount.fullTime": { $gt: 15 } },
      { "staff.employeeCount.partTime": { $gt: 20 } }
    ]
  },
  {
    "name": 1,
    "staff": 1
  }
).limit(2)

The query returns up to two store documents showing only their name and staff details, filtered by employee count criteria.

  {
    "_id": "dda2a7d2-6984-40cc-bbea-4cbfbc06d8a3",
    "name": "Contoso, Ltd. | Home Improvement Closet - Jaskolskiview",
    "staff": {
      "employeeCount": {
        "fullTime": 16,
        "partTime": 8
      }
    }
  },
  {
    "_id": "44fdb9b9-df83-4492-8f71-b6ef648aa312",
    "name": "Fourth Coffee | Storage Solution Gallery - Port Camilla",
    "staff": {
      "employeeCount": {
        "fullTime": 17,
        "partTime": 15
      }
    }
  }

Example 2: Use OR operator as boolean-expression to identify stores with either high sales or large staff

The example finds stores that have either total sales greater than 50,000 or more than 25 total staff members.

db.stores.aggregate([
  {
    $project: {
      name: 1,
      totalSales: "$sales.totalSales",
      totalStaff: { 
        $add: ["$staff.employeeCount.fullTime", "$staff.employeeCount.partTime"] 
      },
      qualifiesForProgram: {
        $or: [
          { $gt: ["$sales.totalSales", 50000] },
          { $gt: [{ $add: ["$staff.employeeCount.fullTime", "$staff.employeeCount.partTime"] }, 25] }
        ]
      }
    }
  },
  { $limit: 4 }
])

The query returns stores that meet either the sales or staffing criteria.

  {
    "_id": "905d1939-e03a-413e-a9c4-221f74055aac",
    "name": "Trey Research | Home Office Depot - Lake Freeda",
    "totalStaff": 31,
    "qualifiesForProgram": true
  },
  {
    "_id": "a715ab0f-4c6e-4e9d-a812-f2fab11ce0b6",
    "name": "Lakeshore Retail | Holiday Supply Hub - Marvinfort",
    "totalStaff": 27,
    "qualifiesForProgram": true
  },
  {
    "_id": "923d2228-6a28-4856-ac9d-77c39eaf1800",
    "name": "Lakeshore Retail | Home Decor Hub - Franciscoton",
    "totalStaff": 13,
    "qualifiesForProgram": false
  },
  {
    "_id": "7e53ca0f-6e24-4177-966c-fe62a11e9af5",
    "name": "Contoso, Ltd. | Office Supply Deals - South Shana",
    "totalStaff": 2,
    "qualifiesForProgram": false
  }

Performance Considerations

  • Review the suggestions for finding better performance.
    • Each condition in the $or array is evaluated independently
    • Use indexes when possible for better performance
    • Consider the order of conditions for optimal execution
    • Use $in instead of $or for multiple equality checks on the same field
    • Keep the number of $or conditions reasonable

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