S表 (SNO,SNAME) 学生关系。SNO 为学号,SNAME 为姓名
C表 (CNO,CNAME,CTEACHER) 课程关系。CNO 为课程号,CNAME 为课程名,CTEACHER 为任课教师
SC表 (SNO,CNO,SCGRADE) 选课关系表。SCGRADE 为成绩问题: 列出“1”号课成绩比“2”号课成绩高的所有学生的学号
大牛请赐教。
C表 (CNO,CNAME,CTEACHER) 课程关系。CNO 为课程号,CNAME 为课程名,CTEACHER 为任课教师
SC表 (SNO,CNO,SCGRADE) 选课关系表。SCGRADE 为成绩问题: 列出“1”号课成绩比“2”号课成绩高的所有学生的学号
大牛请赐教。
INNER JOIN (SELECT * FROM sc WHERE cno=2 AND sno IN(SELECT sno FROM sc WHERE cno=1)) xu
ON (xu.sno=sc.sno)
WHERE sc.cno=1 AND sc.sno IN(SELECT sno FROM sc WHERE cno=2)
AND sc.scgrade>xu.scgrade
CREATE TABLE s(SNO VARCHAR(10),SNAME VARCHAR2(20));
CREATE TABLE c(CNO VARCHAR(10),CNAME VARCHAR2(20),CTEACHER VARCHAR2(10));
CREATE TABLE sc(SNO VARCHAR(10),CNO VARCHAR(10),SCGRADE NUMBER(4));
INSERT INTO s VALUES ('s001','jack');
INSERT INTO s VALUES ('s002','rose');
INSERT INTO s VALUES ('s003','mike');INSERT INTO c VALUES ('1','history','t01');
INSERT INTO c VALUES ('2','English','t02');INSERT INTO sc VALUES ('s001','1',90);
INSERT INTO sc VALUES ('s001','2',80);
INSERT INTO sc VALUES ('s002','1',85);
INSERT INTO sc VALUES ('s002','2',90);
INSERT INTO sc VALUES ('s003','1',80);
INSERT INTO sc VALUES ('s003','2',60);SELECT sno FROM SC t WHERE t.cno='1' AND EXISTS (SELECT 1 FROM SC WHERE sno=t.sno AND cno='2' AND scgrade<t.scgrade);输出:
SNO
s001
s003
where t.sno = d.sno(+)) t where SCGRADE_c>0