A、πC#(C)-πC#(σSNAME='WANG'(S×SC)) SELECT C# FROM C WHERE NOT EXISTS (SELECT * FROM S, SC WHERE S.S#=SC.S# AND SC.C#=C.C# AND SNAME=’WANG’);
B、πC#(C)-πC#(σSNAME='WANG'(S⋈SC)) SELECT C# FROM C WHERE NOT EXISTS (SELECT * FROM S, SC WHERE S.S#=SC.S# AND SC.C#=C.C# AND SNAME=’WANG’);
C、πC#(SC)-πC#(σSNAME='WANG'(S⋈SC)) SELECT C# FROM SC WHERE EXISTS (SELECT * FROM S, SC WHERE S.S#=SC.S# AND SC.C#=C.C# AND SNAME=’WANG’);
D、πC#(C)-πC#(σSNAME='WANG'(S⋈SC)) SELECT C# FROM SC WHERE NOT EXISTS (SELECT * FROM S, SC WHERE S.S#=SC.S# AND SC.C#=C.C# AND SNAME=’WANG’);
第1题
A、π1(σ1=4 ∧ 2≠5(SC?SC)) SELECT DISTINCT X.S# FROM SC AS X, SC AS Y WHERE X.S#=Y.S# AND X.C#!=Y.C#;
B、π1(σ1=4 ∨ 2≠5(SC×SC)) SELECT DISTINCT X.S# FROM SC AS X, SC AS Y WHERE X.S#=Y.S# AND X.C#!=Y.C#;
C、π1(σ1=4 ∨ 2≠5(SC×SC)) SELECT DISTINCT X.S# FROM SC , SC WHERE X.S#=Y.S# AND X.C#!=Y.C#;
D、π1(σ1=4 ∧ 2≠5(SC×SC)) SELECT DISTINCT X.S# FROM SC AS X, SC AS Y WHERE X.S#=Y.S# AND X.C#!=Y.C#;
第2题
A、πC#,CNAME(C×(πS#,C#(SC)÷πS#(S))) SELECT DISTINCT S# FROM SC AS X WHERE EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND NOT EXISTS (SELECT * FROM SC AS Y WHERE Y.S#=X.S# AND Y.C#=C.C#));
B、πC#,CNAME(C×(πS#,C#(SC)÷πS#(S))) SELECT DISTINCT S# FROM SC AS X WHERE NOT EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND NOT EXISTS (SELECT * FROM SC AS Y WHERE Y.S#=X.S# AND Y.C#=C.C#));
C、πC#,CNAME(C×(πS#,C#(SC)÷πS#(S))) SELECT DISTINCT S# FROM SC AS X WHERE NOT EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND NOT EXISTS (SELECT * FROM SC WHERE Y.S#=X.S# AND Y.C#=C.C#));
D、πC#,CNAME(C?(πS#,C#(SC)÷πS#(S))) SELECT DISTINCT S# FROM SC AS X WHERE EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND NOT EXISTS (SELECT * FROM SC AS Y WHERE Y.S#=X.S# AND Y.C#=C.C#));
第3题
A、πS#,C#(SC)÷πC#(σTNAME='LIU'(SC)) SELECT DISTINCT S# FROM SC AS X WHERE NOT EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND NOT EXISTS (SELECT * FROM SC AS Y WHERE Y.S#=X.S# AND Y.C#=C.C#));
B、πS#,C#(SC)÷πC#(σTNAME='LIU'(C)) SELECT DISTINCT S# FROM SC AS X WHERE NOT EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND NOT EXISTS (SELECT * FROM SC AS Y WHERE Y.S#=X.S# AND Y.C#=C.C#));
C、πS#,C#(SC)÷πC#(σTNAME='LIU'(C)) SELECT DISTINCT S# FROM SC AS X WHERE NOT EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND EXISTS (SELECT * FROM SC AS Y WHERE Y.S#=X.S# AND Y.C#=C.C#));
D、πS#,C#(SC)÷πC#(σTNAME='LIU'(C)) SELECT DISTINCT S# FROM SC WHERE NOT EXISTS (SELECT * FROM C WHERE TNAME=’LIU’ AND EXISTS (SELECT * FROM SC AS Y WHERE Y.S#=X.S# AND Y.C#=C.C#));
第4题
A、πCNAME,TNAME(σS#='S3'(SC?C)) SELECT CNAME,TEACHER FROM SC WHERE SC.C#=C.C# AND S#=’S3’
B、πCNAME,TNAME(σS#='S3'(SC?C)) SELECT CNAME,TEACHER FROM SC, C WHERE S#=’S3’
C、πCNAME,TNAME(σS#='S3'(SC×C)) SELECT CNAME,TEACHER FROM SC, C WHERE SC.C#=C.C# AND S#=’S3’
D、πCNAME,TNAME(σS#='S3'(SC?C)) SELECT CNAME,TEACHER FROM SC, C WHERE SC.C#=C.C# AND S#=’S3’;
第5题
A、πSNAME(σSEX='F'∧ TNAME='LIU'(S?SC?C)) SELECT SNAME FROM S, SC, C WHERE S.S#=SC.S# AND SC.C#=C.C# AND SEX=’F’ AND TNAME=’LIU’;
B、πSNAME(σSEX='F'∧ TNAME='LIU'(S?SC?C)) SELECT SNAME FROM S WHERE SEX=’F’ AND NOT EXISTS (SELECT * FROM SC WHERE SC.S#=S.S# AND EXISTS (SELECT * FROM C WHERE C.C#=SC.C# AND TNAME=’LIU’));
C、πSNAME(σSEX='F'∧ TNAME='LIU'(S?SC?C)) SELECT SNAME FROM S WHERE SEX=’F’ AND S# NOT IN (SELECT S# FROM SC WHERE C# IN (SELECT C# FROM C WHERE TNAME=’LIU’));
D、πSNAME(σSEX='F'∨TNAME='LIU'(S?SC?C)) SELECT SNAME (联接查询方式) FROM S, SC, C WHERE S.S#=SC.S# AND SC.C#=C.C# AND SEX=’F’ AND TNAME=’LIU’;
第6题
A、DELETE FROM SC WHERE GRADE IS NULL;
B、DELETE FROM SC;
C、DELETE FROM SC WHERE GRADE = NULL;
D、DELETE FROM SC WHERE GRADE IS NOT NULL;
第7题
S(SNO,SNAME,SEX,AGE,DEPT);
C(CNO,CNAME);
SC(SNO,CNO,SCORE)
其中,S表示学生表。它的各字段以此为学号,姓名、性别、年龄和所在学院;C表示课程表,它的各字段依次为课程号、课程名;SC表示成绩表,它的各字段依次为学号、课程号和分数。
使用SQL语句,查询“计算机学院”所有“男生”的学号,姓名和年龄。
使用SQL语句,查询选修“计算机网络”课程的学生姓名和分数。
使用SQL语句,查询所有课程的课程号以及最高分。
SELECT CNO,MAX(SCORE) FROM SC GROUP BY CNO
请帮忙给出每个问题的正确答案和分析,谢谢!
第8题
S(SNO,SNAME,SEX)
C(CNO,CNAME)
SC(SNO, CNO,SCORE)
其中S表示学生表,各字段依次为学号、姓名、性别;C表示课程表,各字段依次为课程号、课程名;SC表示成绩表,各字段依次为学号、课程号和分数。
使用SQL语句,向学生表增加所处学院SDEP字段,长度为30个字符。
使用SQL语句,查询选修“计算机网络”课程的学生姓名和分数,并按分数降序排序。
使用SQL语句,将课程号为“12”、课程名为“数据库”的一条记录插入C表。
使用SQL语句,将课程号为“12”的课程名修改为“高等数学”。
请帮忙给出每个问题的正确答案和分析,谢谢!
第9题
A、允许查询
B、不允许查询
C、不确定
D、语法有误
第10题
A、允许查询
B、不允许查询
C、不确定
D、语法有误
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