Update the member directory search sql query to check a single custom field, return exact matches

my_pmpro_member_directory_sql_search_where.php

<?php
/*
 * Update the member directory search sql query to check a single custom field.
 * Return results only if the custom field value exactly matches the search term.
 *
 * Replace custom_field_name with your custom field name (meta key).
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_member_directory_sql_search_where( $sql_search_where, $s ) {

	$sql_search_where = "
		AND (
			um.meta_key = 'custom_field_name' AND um.meta_value = '" . esc_sql( $s ) . "'
		)	
	";

	return $sql_search_where;
}
add_filter( 'pmpro_member_directory_sql_search_where', 'my_pmpro_member_directory_sql_search_where', 10, 2 );