题解 | 请写出计算粉丝ctr的sql语句

SELECT read_num/allcount as fans_ctr from (
SELECT sum(show_num) as allcount , count(if (read_num != 0 ,read_num,null )) as read_num  from (
SELECT  c.fans_id ,b.author_id ,  c.content_id  as sing_song, t1.content_id as true_like_song , show_num , read_num  from c
left join b on c.content_id = b.content_id
-- left join a on c.fans_id = a.fans_id

 
left join (
SELECT  a.fans_id , a.author_id , b.content_id from a 
left join b on a.author_id = b.author_id
group by 1,2,3
order by a.fans_id)t1
 on c.fans_id = t1.fans_id
 
where c.fans_id in ((SELECT DISTINCT fans_id from a)) and c.content_id = t1.content_id)t2
)t3