Here's my testing query
SELECT BillableTime
FROM TimeAcctDetail
WHERE u.EmployeeId=17 and Tacode not like '9%'
and Tadate between '04/01/2006' and '04/30/2006'
return 0 record.
SELECT Firstname,lastname,SUM(BillableTime) as BillTime
FROM UserDetail u
LEFT join TimeAcctDetail t
ON...