Oracle SQL查询获取计数

Question

I have a table of different films and every film has some copies:

inventory_id  film_id   store_id
     1           1         1
     2           1         1
     3           2         1
     4           2         1

I need to count the frequency of every film and count the amount of different films taht also have the same amount of copies, Like:

Copies    Counts
  2         2

I wrote this:

select DISTINCT COUNT(*) as Copies, 
       (select COUNT(*) from (select COUNT(*) as Copies from inventory
           group by film_id
           having store_id = 1)
       group by Copies
) as Counts from inventory
where store_id = 1
group by film_id
order by Copies DESC

And the result ist like:

Copies     Counts
   4         73
   3         73
   2         73 

I don't understand why the Counts all have the same value. How can I do it right?

Answer 1

Based on this description:

I need to count the frequency of every film and count the amount of different films that also have the same amount of copies

you would seem to want a histogram of histograms query:

select copies, count(*) as num_films, min(film_id), max(film_id) 
from (select film_id, count(*) as copies
      from inventory
      group by film_id
     ) f
group by cnt
order by cnt;

The following query is doing something quite different, including filtering by store.