Is a user_meta research case-sensitive or not

Question

Solution found : to make a case-sensitive search for a meta_key / meta_value pair : a hardcoded mysql query on the usermeta table with the BINARY keyword, with get_results() method of $wpdb object:

global $wpdb;
$sql = $wpdb->prepare( "SELECT user_id FROM {$wpdb->prefix}usermeta 
                        WHERE meta_key = 'unique_id'    
                        AND BINARY meta_value="unique_id_value"");

$wordpress_user_query = $wpdb->get_results( $sql);