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$cond

The `$cond` operator is used to evaluate a condition and return one of two expressions based on the result. It's similar to the ternary operator in many programming languages.

Syntax

{
   $cond: {
      if: <boolean-expression>,
      then: <true-case>,
      else: <false-case>
   }
}

Parameters

ifobjectrequired

A boolean expression that is evaluated

thenobjectrequired

The expression to return if the `if` condition evaluates to true

elseobjectrequired

The expression to return if the `if` condition evaluates to false

Examples

Determine high sales categories

This query determines if the sales for each category are considered "high" or "low" based on a threshold value of $250,000.

Query:

db.stores.aggregate([{
        $project: {
            _id: 0,
            storeId: "$storeId",
            category: "$sales.salesByCategory.categoryName",
            sales: "$sales.salesByCategory.totalSales",
            salesCategory: {
                $cond: {
                    if: { $gte: ["$sales.salesByCategory.totalSales", 250000] },
                    then: "High",
                    else: "Low"
                }
            }
        }
    },
    { $limit: 3 }
])

Output:

[
    { "sales": [35921, 1000], "category": ["DJ Headphones", "DJ Cables"], "salesCategory": "High" },
    { "sales": [4760], "category": ["Guitars"], "salesCategory": "High" }
]

Determine full-time or part-time dominance

This query determines whether a store employs more full-time or part-time staff.

Query:

db.stores.aggregate([{
        $project: {
            name: 1,
            staffType: {
                $cond: {
                    if: { $gte: ["$staff.totalStaff.fullTime", "$staff.totalStaff.partTime"] },
                    then: "More Full-Time",
                    else: "More Part-Time"
                }
            }
        }
    },
    { $limit: 3 }
])

Output:

[
  { "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5", "name": "Lakeshore Retail | DJ Equipment Stop - Port Cecile", "staffType": "More Full-Time" }
]

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