4．2 对于教学数据库的三个基本表
S（SNO,SNAME,AGE,SEX,SDEPT）
SC（SNO,CNO,GRADE）
C（CNO,CNAME，CDEPT,TNAME）
试用SQL的查询语句表达下列查询：
①检索LIU老师所授课程的课程号和课程名。
②检索年龄大于23岁的男学生的学号和姓名。
③检索至少选修LIU老师所授课程中一门课程的女学生姓名。
④检索WANG同学不学的课程的课程号。
⑤检索至少选修两门课程的学生学号。
select distinct from⑥检索全部学生都选修的课程的课程号与课程名。
⑦检索选修课程包含LIU老师所授(全部)课程的学生学号。
参考答案：
①SELECT CNO，CNAME
FROM    C
WHERE TNAME＝‘LIU’;
②SELECT SNO，SNAME
FROM S
WHERE AGE＞23 AND SEX＝‘M’;
③SELECT SNAME （联接查询方式）
FROM S，SC，C
WHERE S.SNO=SC.SNO AND SC.CNO=C.CNO
AND SEX=’F’ AND TNAME=’LIU’;
或：SELECT SNAME (嵌套查询方式)
FROM S
WHERE SEX＝‘F’
AND SNO IN(SELECT SNO
FROM SC
WHERE CNO IN (SELECT CNO
FROM C
WHERE TNAME=’LIU’));
或：SELECT SNAME (存在量词方式)
FROM S
WHERE SEX＝‘F’
AND EXISTS（SELECT ＊
FROM SC
WHERE SC.SNO=S.SNO
AND EXISTS(SELECT *
FROM C
WHERE C.CNO=SC.CNO
AND TNAME=’LIU’));
④SELECT CNO
FROM C
WHERE NOT EXISTS
(SELECT *
FROM S,SC
WHERE S.SNO=SC.SNO AND SC.CNO=C.CNO
AND SNAME=’WANG’);
或：SELECT CNO
FROM C
WHERE CNO NOT IN
(SELECT SC.CNO
FROM S,SC
WHERE S.SNO=SC.SNO AND SNAME=’WANG’);
或：SELECT CNO
FROM C
WHERE CNO NOT IN
(SELECT CNO
FROM SC
WHERE SNO IN
(SELECT SNO
FROM S
WHERE SNAME=’WANG’));
⑤SELECT DISTINCT X..SNO
FROM SC AS X,SC AS Y
WHERE X.SNO=Y.SNO AND X.CNO<>Y.CNO;
或：SELECT SNO
FROM SC
GROUP BY SNO HAVING COUNT(CNO)>=2;
⑥SELECT CNO,CNAME
FROM C
WHERE NOT EXISTS
(SELECT *
FROM S
WHERE NOT EXISTS
(SELECT *
FORM SC
WHERE SC.SNO=S.SNO AND SC.CNO=C.CNO));
⑦SELECT DISTINCT SNO
FROM SC AS X
WHERE NOT EXISTS
(SELECT *
FORM C
WHERE TNAME=’LIU’
AND NOT EXISTS
(SELECT *
FROM SC AS Y
WHERE Y.SNO=X.SNO AND Y.CNO=C.CNO));
4．3 设有两个基本表R（A，B，C）和S（D，E，F），试用SQL查询语句表达下列关系代数表达式：
①SELECT A FROM R;
②SELECT * FROM R WHERE B=17;
③SELECT * FROM R,S;
④SELECT A,F FROM R,S WHERE C=D;
4．4 设有两个基本表R（A，B，C）和S（A，B，C），试用SQL查询语句表达下列关系代数表达式：
1.(SELECT * FROM R)
UNION
(SELECT * FROM S);
2.(SELECT * FROM R)
INTERSECT
(SELECT * FROM S);
3.(SELECT * FROM R)
EXCEPT
(SELECT * FROM S);
4.(SELECT A,B FROM R)
NATURAL INNER JOIN
(SELECT B,C FROM S);
或：SELECT R.A, R.B, S.C

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