The exposed filter for combined fileds in Drupal 7 seems to work only when entering the exact casing of the search term or phrase used.
Seems a patch is required for this:
- In your Views, Views Handler Filter Combine - /views/handlers/views_handler_filter_combine.inc, find and change the line below (- indicates the original code line, + replacement code of line)
-$expression = "CONCAT_WS(' ', $expression)";
+$expression = "CONVERT(CONCAT_WS(' ', $expression) USING utf8)";