建立信息系选修了1号课程的学生视图，正确的SQL语句为（） A: CREATE VIEW IS_S1 ASSELECT Student.Sno，Sname，Grade FROM Student，SCWHERE Sdept= 'IS' AND Student.Sno=SSno AND SCno= '1'； B: CREATE VIEW IS_S1 (Sno，Sname，Grade) ASSELECT Student.Sno，Sname，Grade FROM Student，SCWHERE Sdept= 'IS' AND SCno= '1'； C: CREATE VIEW IS_S1 (Sno，Sname，Grade) ASSELECT Student.Sno，Sname，GradeFROM Student，SC WHERE Sdept= 'IS' ANDStudent.Sno=SSno AND SCno= '1'

查询学号为201215121的同学选修过的所有课程的名字，不正确的查询语句是： A: SELECT CnameFROM CourseLEFT JOIN SCON Course.Cno = SCnoWHERE Sno = '201215121'; B: SELECT CnameFROM CourseWHERE Cno IN (SELECT CnoFROM SCWHERE Sno = '201215121'); C: SELECT CnameFROM CourseWHERE EXISTS (SELECT *FROM SCWHERE SCno = Course.CnoAND Sno = '201215121'); D: SELECT CnameFROM CourseWHERE NOT EXISTS (SELECT *FROM SCWHERE SCno = Course.CnoAND Sno = '201215121');