第1个回答 2009-09-22
SELECT s1.sno
FROM sc AS s1,sc as s2,c AS c1,c as c2
where s1.cno = c1.cno
and s2.cno=c2.cno
and c1.cname='数据结构'
and c2.cname='C语言'
and s1.sno=s2.sno本回答被提问者采纳
第2个回答 2009-09-22
S(sno,sname,birthday,sdeptartment,tel,sex)
SC(scno,sno,cno,grade)--这里要添个scno也是主键。
C(cno,cname,teacher,pcno)
select s.sno from S s ,SC sc ,C c where s.sno=sc.sno and sc.cno=c.cno and cname in ('数据结构','C语言');
第3个回答 2009-09-23
至少问题:
select s.sno from S a,SC b ,C c where s.sno=b.sno and b.cno=c.cno and cname = '数据结构' and cname='C语言'
至多问题:
select s.sno from S a,SC b ,C c where s.sno=b.sno and b.cno=c.cno and (cname = '数据结构' or cname='C语言')
第4个回答 2009-09-22
这不是书上的例题吗?!
select s.sno from S s ,SC sc ,C c where s.sno=sc.sno and sc.cno=c.cno and (cname = '数据结构' or cname = 'C语言');