Essayez ceci :
SELECT
emp.name AS '## Name',
(SELECT COUNT(*)
FROM project p JOIN employee e ON p.number = e.number
WHERE e.name = emp.name
AND datediff(str_to_date(p.dateEnded, '%Y-%m-%d'), e.dateStarted) = 0
) AS 'Day 0'
,(SELECT COUNT(*)
FROM project p JOIN employee e ON p.number = e.number
WHERE e.name = emp.name
AND datediff(str_to_date(p.dateEnded, '%Y-%m-%d'), e.dateStarted) = 1
) AS 'Day 1'
,(SELECT COUNT(*)
FROM project p JOIN employee e ON p.number = e.number
WHERE e.name = emp.name
AND datediff(str_to_date(p.dateEnded, '%Y-%m-%d'), e.dateStarted) = 2
) AS 'Day 2'
,(SELECT COUNT(*)
FROM project p JOIN employee e ON p.number = e.number
WHERE e.name = emp.name
AND datediff(str_to_date(p.dateEnded, '%Y-%m-%d'), e.dateStarted) = 3
) AS 'Day 3'
,(SELECT COUNT(*)
FROM project p JOIN employee e ON p.number = e.number
WHERE e.name = emp.name
AND datediff(str_to_date(p.dateEnded, '%Y-%m-%d'), e.dateStarted) = 4
) AS 'Day 4'
,(SELECT COUNT(*)
FROM project p JOIN employee e ON p.number = e.number
WHERE e.name = emp.name
AND datediff(str_to_date(p.dateEnded, '%Y-%m-%d'), e.dateStarted) >= 5
) AS 'Day 5'
FROM employee emp
GROUP BY emp.name
Voir Démo SQL Fiddle (- ont émis des hypothèses sur vos données sur la base des informations fournies).
