SSISDB event counts

SELECT
  EventCounts.EventName,
  EventCounts.NumberOfEvents,
  CONVERT(FLOAT,(CONVERT(FLOAT,[NumberOfEvents]) / SUM(NumberOfEvents) OVER ()) * 100) AS 'Percentage'
FROM
  (
    SELECT
      EM.event_name AS 'EventName',
      COUNT(*) AS 'NumberOfEvents'
    FROM SSISDB.catalog.event_messages AS EM
    WHERE EM.event_name IS NOT NULL
    GROUP BY EM.event_name
  ) EventCounts
ORDER BY EventCounts.EventName ASC