设在某SELECT语句的WHERE子句中,需要对Grade列的空值进行处理。下列关于空值的操作,错误的是()。
第1题:
检索选修课程"C2”的学生中成绩最高的学生的学号,正确的SELECT语句是______。
A.SELECT S# FORM. SC WHERE C#="C2"AND GRADE>=(SELECT GRADE FORM. SC WHERE C#="C2")
B.SELECT S# FORM. SC WHERE C#="C2"AND GRADE IN(SELECT GRADE FORM. SC) WHERE C#="C2"
C.SELECT S# FORM. SC WHERE C#="C2"AND GRADE NOT IN(SELECT GRADE FORM. SC WHERE C#="C2")
D.SELECT S# FORM. SC WHERE C#="C2"AND GRADE>=ALL(SELECT GRADE FORM. SC WHERE C#="C2")
第2题:
实现“从学生信息表中找出性别为女的学生姓名”的SQL语句是
A.SELECT*FROMs
B.SELECT*FROM s WHERE sex='女'
C.SELECT sname FROM s WHERE sex='女'
D.SELECT*FROM s WHERE grade="
第3题:
关系SC(Sno,Cno,Grade)表示学号,课程号,成绩。现要查询平均分在90分以上的学生的学号和平均成绩,正确的语句是______。
A.SELECT Sno,AVG(Grade) FROM SC WHERE AVG(Grade)>=90 GROUP BY Sno
B.SELECT Sno,AVG(Grade) FROM SC GROUP BY Sno HAVING AVG(Grade)>=90
C.SELECT Sno,AVG(Grade) FROM SC WHERE AVG(Grade)>=90 ORDER BY Sno
D.SELECT Sno,AVG(Grade) FROM SC GROUP BY Cno HAVING AVG(Grade)>=90
第4题:
“从学生选课信息表中找出无成绩的元组”的SQL语句是( )。 A.SELECT*FROM sc WHERE grade=NULL B.SELECT*FROM sc WHERE grade IS'' C.SELECT*FROM sc WHERE grade IS NULL D.SELECT*FROM sc WHERE grade=''
第5题:
基于学生.课程数据库中的三个基本表:
学生信息表:s (snumber, sname, sex, age, dept)主码为snumber
课程信息表:c(cnumber, cname,teacher)主码为cnumber
学生选课信息表:sc(snumber, cnumber, grade)主码为(snumber, cnumber)
“从学生选课信息表中找出无成绩的元组”的SQL语句是( )。
A)SELECT ﹡FROM sc WHERE grade=NULL
B)SELECT﹡FROM sc WHERE grade IS "
C)SELECT﹡FROM sc WHERE grade IS NULL
D)SELECT﹡FROM sc WHERE grade=''
第6题:
已知关系模式:sc(sno, sname, grade),各属性含义依次为学号、课程名、分数。要查找“数据库”课分数最高的学生的学号,正确的SQL语句是
A.SELECT sno FROM sc WHERE sname="数据库" AND grade=MAX(grade)
B.SELECT sno FROM sc FOR sname="数据库" OR grade>=MAX(grade)
C.SELECT sno FROM sc WHERE sname="数据库" AND grade=(SELECT MAX(grade) FROM sc
D.SELECT sno FROM sc FOR sname="数据库" OR grade=(SELECT MAX (grade) FROM sc
第7题:
有如下的SQL语句:
Ⅰ.SELECT sname FROMs,sc WHERE grade<60
Ⅱ.SELECT sname FROMs WHERE sno IN(SELECT sno FROM sc WHERE grade<60
Ⅲ.SELECT sname FROMs,sc WHERE s.sno=Sc.sno AND grade<60
若要查找分数(grade)不及格的学生姓名(sname),以上正确的有哪些? ( )
A.Ⅰ和Ⅱ
B.Ⅰ和Ⅲ
C.Ⅱ和Ⅲ
D.Ⅰ、Ⅱ和Ⅲ
第8题:
有如下的SQL语句: Ⅰ. SELECT sname FROM s, sc WHERE grade60 Ⅱ. SELECT sname FROM s WHERE sno IN(SELECT sno FROM sc WHERE grade60) Ⅲ. SELECT sname FROM s, sc WHERE s.sno=sc.sno AND grade60 若要查找分数(grade)不及格的学生姓名(sname),以上正确的有哪些?( )。
A.Ⅰ和Ⅱ
B.Ⅰ和Ⅲ
C.Ⅱ和Ⅲ
D.Ⅰ、Ⅱ和Ⅲ
第9题:
已知学生选课信息表:sc(sno,cno,grade)。查询“至少选修了一门课程,但没有学习成绩的学生学号和课程号”的SQL语句是
A.SELECT sno,cno FROM sc WHERE grade=NULL
B.SELECT sno,cno FROM sc WHERE grade IS‘’
C.SELECT sno,cno FROM sc WHERE grade IS NULL
D.SELECT sno,cno FROM sc WHERE grade=‘’
第10题:
查找学生姓名及其所选修课程的课程号和成绩,正确的SQL语句是
A.SELECT sname FROM student,SELECT cno,grade FROM sc WHERE student.sno=sc.sno
B.SELECT sname,cno,grade FROM student,course WHERE student.sno=course.cno
C.SELECT sname,cname,grade FROM student,course,sc WHERE student.sno=sc.sno and sc.cno=course,cno
D.SELECT sname,cno,grade FROM student,sc WHERE student.sno=sc.sno