问题
单项选择题
(33)~(34)题的关系代数操作基于如下的关系R和S: |
查询选修了课程号为’C2’的学号和姓名,若用下列SQL的SELECT语句表达时,哪一个是不正确的 ( )
A.SELECT S#,SNAMEFROMS WHERE S#=(SELECTSS# FROMSC WHERE C#=’C2’
B.SELECTS#,SNAMEFROMS,SC WHERES#=SS# AND C#=’C2’
C.SELECTS#,SNAME FROM S,SC WHERES#=SS# AND C#=’C2’ORDER BY S#
D.SELECTS#,SNAME FROM S WHERE S# IN (SELECT S S# FROM SC WHERE C#=’C2’
答案
参考答案:A