select distinct custid
from product_details
where prodid in (1,4) and custid not in (select custid from product_details where prodid=0)
Nope that wont work the IN works like an OR so CustID 2 is returned in the result set..
Andy
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A computer lets you make more mistakes faster than any invention in human history - with the possible exceptions of handguns and tequila. Mitch Ratcliffe