Count

The Count function is a numeric aggregate function that returns the number of elements in a collection that satisfy an optional criteria. It can count all elements in a collection or only those that meet a specified condition.

Function Name: Count

Return Type: Number (Double)

Syntax

The Count function can be called with the following syntax:

Syntax 1 - Count All Elements:

Count(collection)

Syntax 2 - Count with Criteria:

Count(collection, criteria)

Named Parameter Syntax:

Count(collection -> <collection_expression>, criteria -> <lambda_expression>)

Parameters

Parameter

Type

Required

Description

collection

Collection

Yes

The collection of elements to count. Can be an array, query result, or any collection expression.

criteria

Lambda

No

A lambda expression that defines a condition for counting. Takes one parameter representing the current element and returns a boolean. If omitted, counts all elements in the collection.

Return Value

  • Type: Number (double precision)

  • Returns:

    • The total number of elements in the collection if no criteria is specified

    • The number of elements that satisfy the criteria if a criteria lambda is provided

    • 0 if the collection is empty

    • 0 if no elements satisfy the criteria

Evaluation Rules

The Count function follows these evaluation rules:

  1. No Criteria: When criteria is omitted, returns the total count of elements without iteration

  2. With Criteria: When criteria is provided, evaluates each element and counts those where the criteria returns true

  3. Empty Collections: Returns 0 for empty collections

  4. Null/Undefined Handling: Null or undefined values are passed to the criteria lambda; the lambda determines whether to count them

  5. Boolean Criteria: When provided, the criteria lambda must return a boolean value

  6. Complete Iteration: Unlike Any or All, Count always processes all elements to get an accurate count

  7. Order Independence: The order of elements doesn’t affect the count

Use Cases

The Count function is useful for:

  • Size Metrics: Determining the number of elements in filtered collections

  • Statistical Analysis: Counting occurrences of specific conditions

  • Validation: Verifying expected quantities of items

  • Business Metrics: Calculating KPIs like “number of active customers”

  • Data Quality: Counting missing, invalid, or exceptional data points

  • Conditional Reporting: Generating counts based on complex conditions

Examples

{
  "Comment_Count_1": "Retrieve count of all employees older than 40 with salary greater than 100000.",
  "Count_1": "$value(Count(Companies.Select(c => c.Employees.Where(e => e.Age >= 40 && e.Salary > 100000))))",

  "Comment_Count_2": "Another way to Retrieve count of all employees older than 40 with salary greater than 100000.",
  "Count_2": "$value(Count(Companies.Select(c => c.Employees).Where(e => e.Age >= 40), e => e.Salary > 100000))",

  "Comment_Count_3": "Demo of using named parameters to make the intent clear.",
  "Count_3": "$value(Count(collection -> Companies.Select(c => c.Employees), criteria -> e => e.Age >= 40 && e.Salary > 100000))"
}