Postgresql:如何正确计算百分比?

从我的数据库。

select genre,count(*) from titles group by genre order by count desc;
     genre       | count 
-----------------+-------
 Drama           |   529
 Comic           |   393
 Martial arts    |   276
 History         |   269
 Action          |   237

我的问题是:如何获得百分比? 我想要这样的东西

select ??????;
     genre       | percentage 
-----------------+-------
 Drama           |   30%
 Comic           |   20%
 Martial arts    |   20%
 History         |   15%
 Action          |   11%
 Other           |   4%

在询问之前,我已经尝试了很多从gogle和stackexchange获取的代码,正如您从psql历史中看到的那样 但所有的失败都是错误的或非常奇怪的结果。

SELECT
    title,
    ROUND( AVG( genre ), 2 ) percentage
FROM
    titles
INNER JOIN genre
        USING(id_genre)
GROUP BY
    title
ORDER BY
    genre DESC;


select title, round ( AVG( genre ), 2 ) percentage from titles;


SELECT round((count(genre) *100)::numeric / NULLIF(count(*), 0), 2) AS percentage;