make-list-if-aggregation-function.md

title	description	ms.reviewer	ms.topic	ms.date
make_list_if() (aggregation function)	Learn how to use the make_list_if() aggregation function to create a dynamic JSON object of expression values where the predicate evaluates to true.	alexans	reference	11/13/2023

make_list_if() (aggregation function)

Creates a dynamic array of expr values in the group for which predicate evaluates to true.

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[!INCLUDE data-explorer-agg-function-summarize-note]

Syntax

make_list_if(expr, predicate [, maxSize])

[!INCLUDE syntax-conventions-note]

Parameters

Name	Type	Required	Description
expr	string	✔️	The expression used for the aggregation calculation.
predicate	string	✔️	A predicate that has to evaluate to true in order for expr to be added to the result.
maxSize	integer		The maximum number of elements returned. The default and max value is 1048576.

Returns

Returns a dynamic array of expr vlaues in the group for which predicate evaluates to true. If the input to the summarize operator isn't sorted, the order of elements in the resulting array is undefined. If the input to the summarize operator is sorted, the order of elements in the resulting array tracks that of the input.

Example

The following example shows a list of names with more than 4 letters.

[!div class="nextstepaction"] Run the query

let T = datatable(name:string, day_of_birth:long)
[
   "John", 9,
   "Paul", 18,
   "George", 25,
   "Ringo", 7
];
T
| summarize make_list_if(name, strlen(name) > 4)

Output

list_name
["George", "Ringo"]

Related content

make_list function, which does the same, without predicate expression.