oracle選取出現次數最多的前５條數據

SELECT
	*
FROM
	(
		SELECT
			PROJECT_LISTING.MATERIAL,
			COUNT (*) AS "出現次數"
		FROM
			PROJECT_LISTING
		WHERE
			PROJECT_LISTING.MATERIAL IS NOT NULL
		GROUP BY
			PROJECT_LISTING.MATERIAL
		ORDER BY
			COUNT (*) DESC
	) WHERE　ROWNUM <= 5

	ORDER BY
			COUNT (*) DESC　是關鍵排序

COUNT (*) AS "出現次數"　　這個可以不寫，只是為了看的明白