说明: 1.The results of s-r: A B C b g a 2. ( SELECT MemNo FROM MEMBER, BOOK WHERE MemNo = BorrowerMemNo AND CallNumber = 'QA76.9.D26C66' ) Except ( SELECT MemNo FROM MEMBER, BOOK WHERE MemNo = BorrowerMemNo AND CallNumber = 'QA76.9.D7E53' ); The results:
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