Get 0 value from a count with no rows

Question

I have SELECT:

SELECT c FROM (
    SELECT "candidate_id" as id, count("candidate_id") as c
    FROM "Applicaions"
    GROUP BY &         


        

Answer 1

You can't.

If your candidate has no applications, then you have no way to read their candidate_id value

How would you have knowledge that a candidate exists without them being in the Applications table?

In your example code, there is no candidate and therfore you couldn't possible say that a specific candidate had zero applications. By that logic there are an infinite number of candidates having zero applications.

You will need a table of candidates in order to derive this information... unless your intention is to presume a candidate exists because you're asking for it by ID?

EDIT

Now that you have a Candidates table you can do this:

SELECT c.ID, (SELECT COUNT(a.*) FROM Applications a WHERE a.candidate_id = c.ID) 
FROM Candidate c
WHERE ....