How to: SELECT from multiple CTEs that are mutually exclusive - sql

Question

I am in a situation where I need to show stats of a user based on referrals that user made & then stats about those referred users' activities. So, if user A refers user B, C then it means user A referred 2 users. Now, I need to get how many of those referred users did take an action i.e. PURCHASED. But they may not purchase which counts to 0. I have following query using CTEs which does work as expected but it also returns some false negative results. i.e.
WITH direct_referrals AS (
SELECT id
FROM "user"
WHERE "user"."referredBy" = ${userId}
),
application_stats AS (
SELECT count(status), status
FROM "application"
WHERE "userId" IN (SELECT id FROM direct_referrals)
GROUP BY status
)
SELECT *, (SELECT count(id) FROM direct_referrals) AS "totalReferrals"
FROM application_stats;
This query returns correct result if at-least 1 referred user took some action but it fails when none has taken any action in which case this query returns the referred users to be 0 which is not true.
I can see that SELECT is dependent on application_stats CTE which may not return any result & hence the direct_referrals are also not returned. I am somewhat new to SQL so don't really know many options. Any help is appreciated.
Thanks
Update with sample Data & Expected Results
// User model
Id username referredBy
---- -------- -------------------
1 jon NULL
2 jane 1
3 doe 1
4 smith 2
5 john 1
// Application model
Id userId status
---- -------- -------------------
1 12 'APPLIED'
2 13 'APPLIED'
3 14 'VIEWED'
Expected Result (for userId = 1):
User (referral) stats Application stats
------------------- -------------------
3 0
Actual Result:
User (referral) stats Application stats
------------------- -------------------
0 0

Answer 1

Something like this should give you what you want:
WITH REFERRAL AS (
SELECT REFERREDBY, COUNT(USERNAME) AS "REF_CNT"
FROM USER_MODEL
WHERE REFERREDBY IS NOT NULL
GROUP BY REFERREDBY
),
APPLICATIONS AS (
SELECT UM.REFERREDBY, COUNT(ML.APPL_STATUS) AS "APPL_CNT"
FROM USER_MODEL UM
LEFT OUTER JOIN APPLICATION_MODEL ML ON UM.ID = ML.USER_ID AND ML.APPL_STATUS = 'PURCHASED'
GROUP BY UM.REFERREDBY
)
SELECT R.REFERREDBY, R.REF_CNT, A.APPL_CNT
FROM REFERRAL R
LEFT OUTER JOIN APPLICATIONS A ON R.REFERREDBY = A.REFERREDBY;