select m.member_no, m.lastname, 
	ISNULL(convert(varchar(30), c.charge_amt) , 'No Sales')
from member AS m
	LEFT OUTER JOIN charge AS c ON m.member_no = c.member_no
where m.member_no < 100 and c.charge_amt IS NULL

select m.member_no, m.lastname, c.charge_amt
from member m, charge c
where m.member_no *= c.member_no
and c.charge_amt IS NULL