Computing conversion rate by counting TRUE/FALSE statements - sql

Question

Sorry if this sounds very basic; bear with me.
I need to determine the conversion rate of 3 ads, each representing a product; that would be subscription divided by the number of people who clicked the ad.
COLUMNS:
person_id - unique identifier of the person
date - date they were shown the ad
ad_id - content of the ad: ad_1_product1, ad_2_product2, or ad_3_product3
clicked (TRUE/FALSE) - clicked on the ad
signed_up - (TRUE/FALSE) created an account
subscribed (TRUE/FALSE) - started a paid subscription
I set clicked, signed_up and subscribed as boolean.
MY CODE:
SELECT ad_id, (count(subscribed) / count(clicked)) as CR
FROM videoadcampaign
WHERE subscribed = 'TRUE' AND clicked = 'TRUE'
GROUP BY ad_id;
Of course, the code above gives me a ratio of 1, because SQL is still counting the total and dividing by the same number because of those conditions.
I am totally stuck.
I will also need to calculate other KPIs for clicks and signed_up, so filtering those booleans and put them into a ratio is the core of what I need to do.
Is there a way I can tell SQL to compute CR = SUBS (TRUE) / SUBS (TRUE + FALSE) [or total count] and then filter by CLICK = TRUE?
Thank you tons for your help!

Answer 1

It depends on your database, but the general notion would be:
SELECT ad_id,
(SUM(CASE WHEN subscribed = 'TRUE' THEN 1.0 ELSE 0 END) /
SUM(CASE WHEN clicked = 'TRUE' THEN 1 ELSE 0 END)
) as CR
FROM videoadcampaign
GROUP BY ad_id;
In many databases, you can do something like this if the columns are integers (0 = false, 1 = true):
SELECT ad_id, SUM(subscribed) / SUM(clicked) as CR
FROM videoadcampaign
WHERE clicked = 'TRUE'
GROUP BY ad_id;
Or even:
SELECT ad_id, AVG(subscribed) as CR
FROM videoadcampaign
WHERE clicked = 'TRUE'
GROUP BY ad_id;