sql对某一列进行频数统计容易，但是进行频率统计就不是那么直接了。分享一下从频数统计到频率统计的转化：

频数统计
SELECT top.id, Count(*) AS 频数
FROM [top]
GROUP BY top.id;

频率统计

SELECT top.id, round(Count(*)/(SELECT count(top.id) AS count FROM [top]),2) AS 频率
FROM [top]
GROUP BY top.id;