Include 0 when using count() SQL Server Left Join not working - sql

Question

Here I have used a left join on the person table because I want to include every record in that table even if it doesn't have an associated record in the task table. How can I resolve this to include the 0's in my results?
SELECT CONVERT(NVARCHAR, COUNT(p.personID)) AS count,
CONVERT(DECIMAL(4, 2), 1.0 * COUNT(p.personID) / DATEDIFF(DAY, #startDate, #endDate)) AS average,
p.personID,
p.firstname,
p.lastname,
c.companyname
FROM Tasks t
LEFT JOIN Person p
ON p.personID = t.personID
JOIN Client c
ON c.id = p.employer
JOIN Commission m
ON m.ClientID = c.ID
WHERE t.created BETWEEN #startDate AND #endDate
AND m.owner IN ( 'John Doe' )
GROUP BY p.personID,
p.firstname,
p.lastname,
c.companyname
ORDER BY c.companyname,
count DESC

Answer 1

I just figured out the answer to my problem... because I put conditions in the where clause on behalf of the other tables that I joined, it filtered out what I wanted. So I changed the person table to the "driving table" and I took the conditions from the where clause and put them in the join statement as I was joining the tasks table as follows:
SELECT
convert(nvarchar, COUNT(t.personID)) AS count,
CONVERT(decimal(4, 2), 1.0*COUNT(t.personID)
/ DATEDIFF(DAY, #startDate, #endDate)
) AS average,
p.personID,
p.firstname,
p.lastname,
c.companyname
FROM Person p
LEFT JOIN Tasks t
ON t.personID = p.personID AND t.created BETWEEN #startDate AND #endDate
JOIN Client c
ON c.id = p.employer
JOIN Commission m
ON m.ClientID = c.ID AND m.owner IN ('John Doe')
GROUP BY p.personID, p.firstname, p.lastname, c.companyname
ORDER BY c.companyname, count DESC

Answer 2

Provide filtered input through a subquery instead of the WHERE clause:
SELECT
convert(nvarchar, COUNT(p.personID)) AS count,
CONVERT(decimal(4, 2),1.0*COUNT(p.personID) / DATEDIFF(DAY, #startDate, #endDate)) AS average,
p.personID,
p.firstname,
p.lastname,
c.companyname
FROM Person p
LEFT JOIN (
select personId from tasks
where t.created BETWEEN #startDate AND #endDate
) t
ON t.personID = p.personID
JOIN Client c
ON c.id = p.employer
JOIN Commission m
ON m.ClientID = c.ID AND m.owner IN ('John Doe')
GROUP BY p.personID, p.firstname, p.lastname, c.companyname
ORDER BY c.companyname, count DESC
Maybe not the most useful in this particular example, but if the WHERE clause is complex and filtering more than one table, this is the answer.