SQL> select name,bdate from reader,borrow,book where
  2  reader.rno=borrow.rno and borrow.bno=book.bno and book.title='database management';

NAME       BDATE
---------- --------------
qian       02-11月-04
zhou       02-5月 -04

SQL> select rno from borrow where bno in (select bno from book where title='thinking in Java');

RNO
----
1002

SQL> select name from reader where rno in (select rno from borrow where bno in (select bno from book where title='thinking in Java'));

NAME
----------
qian

SQL> select name,bdate,title from reader,borrow,book where reader.rno=borrow.rno and borrow.bno=
  2  book.bno and name='zheng' and bdate>'01-1月-06';

未选定行

SQL> select 'zhangsan',count(*) from borrow,reader where borrow.rno=reader.rno and reader.name='zhangsan';

'ZHANGSA   COUNT(*)
-------- ----------
zhangsan          0

或用分组也可以，分组属性用reader.rno还是用name含义不同。

SQL> select '1003',sum(price) from borrow,book where borrow.bno=book.bno and borrow.rno='1003';

'100 SUM(PRICE)
---- ----------
1003         64

SQL>