If I add 'j.suspended' as here:
jobs AS j
j.expire > NOW() AND
j.suspended IS NULL
It will return NULL for all fields of the "suspended" column, even if some entries are not NULL (those that are marked suspended by a datetime entry should be not null).
The AND in the query means it should return records where both conditions are true: j.expire > NOW() and j.suspended IS NULL. That means all of the records returned have j.suspended is null.
My intention is clear to display just those jobs that did not expired and are not suspended.
I think that's what you're doing here. You're getting jobs where expire is after now and suspended is null.
If that's not what you want, can you explain in a little more detail what you want? I may not understand.