Unable to get a join to pull all records from another table in MySQL
The problem is this:

If r.dateReceived is NULL, the WHERE r.dateReceived &gt; 1587574487 is never satisfied

What you need to do is check for r.dateReceived in the WHERE clause as well

SELECT r.dateReceived as Date,
t.empNumber AS Emp,
r.grpNumber AS Grp,
r.empFName,
r.empLName 
FROM empInfo t 
LEFT JOIN empreports r 
ON t.empNumber = r.empNum
WHERE t.grpNumber = 100 
AND t.active = 1 
AND (r.dateReceived &gt; 1587574487 OR r.dateReceived IS NULL)
ORDER BY CAST(t.empNumber as UNSIGNED INTEGER) ASC


GIVE IT A TRY !!!