SQL 查询之间的数学运算符

Question

I'm wondering what the best method would be of using two separate query results in a mathematical operation.

select count(*) as french_films
from language l 
join film f on l.language_id = f.original_language_id
where l.name = 'French'
group by l.name

select count(*) as non_english_films
from language l 
join film f on l.language_id = f.original_language_id
where l.name != 'English'

The code itself produces a result of 12 for the first query and 59 for the second query.

I want to express the 1st number (12) as a percentage of the 2nd (59) which should be around 20.34%.

I've attempted this as 2 separate CTEs however am struggling on what is best to join them on or if that is the best method.

Thank you in advance for your help.

Answer 1

Use conditional aggregation:

select sum(case when l.name = 'French' then 1 else 0 end) as french_films,
       sum(case when l.name <> 'English' then 1 else 0 end) as non_english_films
from language l join
     film f
     on l.language_id = f.original_language_id;