Customers who placed no orders: Step 1 + result of custid match
match?	custid	city	orderid	custid
———	———	———	———	———
TRUE	A	Seattle	1	A
FALSE	A	Seattle	2	B
FALSE	A	Seattle	3	B
FALSE	A	Seattle	4	B
UNKNOWN	A	Seattle	5	NULL
FALSE	B	Seattle	1	A
TRUE	B	Seattle	2	B
TRUE	B	Seattle	3	B
TRUE	B	Seattle	4	B
UNKNOWN	B	Seattle	5	NULL
FALSE	C	Seattle	1	A
FALSE	C	Seattle	2	B
FALSE	C	Seattle	3	B
FALSE	C	Seattle	4	B
UNKNOWN	C	Seattle	5	NULL
FALSE	D	Denver	1	A
FALSE	D	Denver	2	B
FALSE	D	Denver	3	B
FALSE	D	Denver	4	B
UNKNOWN	D	Denver	5	NULL