现要查找缺少成绩(Grade)的学生学号(Snum),相应的SQL语句是

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现要查找缺少成绩(Grade)的学生学号(Snum),相应的SQL语句是

A.SELECTSnumFROMSCWHEREGrade=0

B.SELECTSnumFROMSCWHEREGrade<=0

C.SELECTSnumFROMSCWHEREGrade=NULL

D.SELECTSnumFROMSCWHEREGradeISNULL

参考答案:

答案:SELECTSnumFROMSCWHEREGradeISNULL