查询如下：
select MemNo
from Member
where MemNo not in (select BorrowerMemNo from Book)
表和数据如下：
CREATE TABLE Member(
MemNo NUMERIC(20) NOT NULL,
DriverLicState VARCHAR(20),
DriverLicNo VARCHAR(40),
Fname VARCHAR(20),
MI VARCHAR(10),
Lname VARCHAR(20),
Address VARCHAR(250),
PhoneNumber VARCHAR(15),
PRIMARY KEY (MemNo));
----------------------------------------------------
CREATE TABLE Book(
Book_ID NUMERIC(20) NOT NULL,
Edition VARCHAR(80),
BorrowerMemNo NUMERIC(20),
BorrowDueDatetime DATETIME,
CallNumber VARCHAR(40),
LibCheck NUMERIC(20),
PRIMARY KEY (Book_ID),
FOREIGN KEY (CallNumber) REFERENCES Title(CallNumber),
FOREIGN KEY (BorrowerMemNo) REFERENCES Member(MemNo),
FOREIGN KEY (LibCheck) REFERENCES Librarian(SSN));
----------------------------------------------------------
INSERT INTO Member VALUES (123, 'PA', '123', 'John', '', 'Summers', '4615 Forbes Ave, Pittsburgh, PA 15213', '412-268-0001');
INSERT INTO Member VALUES (124, 'GA', '124', 'Jon', '', 'Butterworth', '10 Fifth Ave, Atlanta, GA 30332', '404-894-0001');
INSERT INTO Member VALUES (125, 'PA', '125', 'Susan', 'B', 'Carlione', '4600 Verona Road, Pittsburgh, PA 15217', '412-200-0001');
INSERT INTO Member VALUES (126, 'NC', '126', 'Mohammed', '', 'Ismail', '250 Peachtree Street, Salem, NC 15213', '421-268-0001');
INSERT INTO Member VALUES (127, 'PA', '127', 'Asterio', '', 'Tanaka', '415 Craig Street, Pittsburgh, PA 15213', '412-220-0001');
--------------------------------------------------------------
INSERT INTO Book VALUES (123, '1', 123, '2000-12-12', 'Call123', 202);
INSERT INTO Book VALUES (223, '1', 125, '2000-11-11', 'Call123', 201);
INSERT INTO Book VALUES (124, '1', 124, '2000-06-09', 'Call124', 201);
INSERT INTO Book VALUES (224, '1', 125, '2000-11-11', 'Call124', 201);
INSERT INTO Book VALUES (125, '1', 125, '2000-11-11', 'Call125', 201);
INSERT INTO Book VALUES (225, '1', NULL, NULL, 'Call125', NULL);
INSERT INTO Book VALUES (126, '1', 125, '2000-11-11', 'Call126', 201);
INSERT INTO Book VALUES (226, '1', 124, '2000-06-09', 'Call126', 202);
INSERT INTO Book VALUES (326, '1', 124, '2000-06-09', 'Call126', 202);
INSERT INTO Book VALUES (127, '1', NULl, NULL, 'Call127', NULL);
INSERT INTO Book VALUES (128, '1', 125, '2000-11-11', 'Call128', 201);
INSERT INTO Book VALUES (228, '1', 126, '2000-10-10', 'Call128', 202);
INSERT INTO Book VALUES (129, '1', 123, '2000-12-12', 'Call129', 202);
INSERT INTO Book VALUES (229, '1', 125, '2000-12-12', 'Call129', 202);
部分数据没有用，请问为什么这个结果是空呢？？？
用的是SQL 2012
------解决方案--------------------
你把BorrowerMemNo 是null得那两行去掉试试
------解决方案--------------------
楼主啊，你的这个ＳＱＬ语句，结果本来就是空啊。
Ｍember表中的memno在表Book中都有啊。
所以必然为空啊。
------解决方案--------------------
BorrowerMemNo有NULL值，加上对NULL值的判断