SQL statement - one result to be divided with another

Question

I'm very new to this SQL world so it might be a dumb question.

I have this table "page_load" with, amongst others, the columns "page_title","user_id" and "utm_source". I can view the total of distinct "user_id" with filter on "page_title" with this simple code:

SELECT count(distinct "page_load"."user_id")
FROM "page_load"
WHERE "page_title" = 'Discover'

And I can view another filter with this one:

SELECT count(distinct "page_load"."user_id")
FROM "page_load"
WHERE "utm_source" = 'recommend"

Well, can I get the second result to be divided by the first?

This way I can get the percentage of the second based on the first on a SQL question.

Answer 1

Use a ratio with conditional aggregation:

SELECT 100.0 * COUNT(DISTINCT CASE WHEN utm_source = 'recommend' THEN user_id END) /
               COUNT(DISTINCT CASE WHEN page_title = 'Discover' THEN user_id END)
FROM page_load
WHERE utm_source = 'recommend' OR page_title = 'Discover';