in

This page explains how to use the in operator in APL.

The in operator in APL filters records based on whether a value matches any element in a specified set using case-sensitive comparison. Use this operator to check if a field value equals one of several values, which is more concise and efficient than chaining multiple equality checks with or. The in operator works with any scalar type, including strings, numbers, booleans, datetime values, and dynamic arrays.

Use the in operator when you need exact case-sensitive matching against multiple values, such as filtering logs by specific status codes, identifying requests from particular regions, or isolating traces from a subset of services.

Usage

Syntax

APL

Expression in (Value1, Value2, ...)

Parameters

Name	Type	Required	Description
Expression	scalar	Yes	The value to find in the given set.
Value	scalar or tabular	Yes	The values to compare against the expression. Specify individual scalar values, a dynamic array, or a subquery. When using a subquery with multiple columns, APL uses the first column. The operator supports up to 1,000,000 unique values in the set.

Returns

Returns true if the expression value is found in the specified set. Returns false otherwise.

Use case examples

Filter HTTP logs to find requests with successful status codes.

Query

APLRun in Playground

['sample-http-logs']
| where status in ('200', '201', '204')
| project _time, method, uri, status

Output

_time	method	uri	status
2024-10-17 10:15:00	GET	/api/users	200
2024-10-17 10:16:30	POST	/api/data	201
2024-10-17 10:17:45	DELETE	/api/item	204

This query filters the HTTP logs to return only requests that resulted in successful status codes (200, 201, or 204), helping you focus on completed requests.

Identify traces from specific services in your microservices architecture.

Query

APLRun in Playground

['otel-demo-traces']
| where ['service.name'] in ('frontend', 'checkout', 'cart')
| project _time, trace_id, ['service.name'], kind, duration

Output

_time	trace_id	service.name	kind	duration
2024-10-17 11:00:00	abc123	frontend	server	45ms
2024-10-17 11:00:05	def456	checkout	server	120ms
2024-10-17 11:00:10	ghi789	cart	client	30ms

This query filters traces to show only spans from the frontend, checkout, and cart services, helping you analyze traffic flow through critical user-facing services.

Use with dynamic arrays

When you pass a dynamic array with nested arrays, APL flattens them into a single list. For instance, x in (dynamic([1, [2, 3]])) is equivalent to x in (1, 2, 3).

APL

let methods = dynamic(['GET', 'POST']);
['sample-http-logs']
| where method in (methods)

!in: Use for case-sensitive matching to exclude values. Returns true if the value isn't in the set.
in~: Use for case-insensitive matching. Matches values regardless of case.
!in~: Use for case-insensitive exclusion. Excludes values regardless of case.
where: Use to filter rows based on conditions. The in operator is commonly used within where clauses.
has_any: Use for term matching against multiple values. Unlike in which checks for exact equality, has_any checks if a string contains any of the specified terms.