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SELECT*FROM sc WHERE grade=NULL SELECT*FROM sc WHERE grade IS’’ SELECT*FROM sc WHERE grade IS NULL SELECT*FROM sc WHERE grade=’’
学生信息表s 学生信息表S和课程信息表c 学生信息表S、课程信息表c和学生选课信息表sc 学生信息表S和学生选课信息表sc
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SELECT sno, cno FROM SC WHERE grade=NULL SELECT sno, cno FROM SC WHERE grade IS" SELECT sno, cno FROM SC WHERE grade IS NULL SELECT sno, cno FROM SC WHERE grade="
学生信息表s 学生信息表s和课程信息表c 学生信息表s、课程信息表c和学生选课信息表sc 学生信息表s和学生选课信息表sc
学生信息表s 学生信息表s和课程信息表c 学生信息表s、课程信息表c和学生选课信息表sc 学生信息表s和学生选课信息表sc
SELECT * FROM sc WHERE grade=NULL SELECT * FROM sc WHERE grade IS" SELECT* FROM sc WHERE grade IS NULL SELECT* FROM sc WHERE grade="
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SELECT sno,cno FROM SC WHERE grade=NULI SELECT sno,cno FROM SC WHERE grade Is SELECT sno,cno FROM SC WHERE grade IS NULL SELECT sno,cno FROM SC WHERE grade="
SELECT * FROM sc WHERE grade=NULL SELECT * FROM sc WHERE grade IS “ ” SELECT * FROM sc WHERE grade=‘ ’ SELECT * FROM sc WHERE grade IS NULL
SELECT * FROM sc WHERE grade=NULL SELECT * FROM sc WHERE grade IS ‘ ’ SELECT * FROM sc WHERE grade IS NULL SELECT * FROM sc WHERE grade =‘ ’
学生信息表s 学生信息表s和课程信息表c 学生信息表s、课程信息表c和学生选课信息表sc 学生信息表s和学生选课信息表sc
SELECT * FROM sc WHERE grade=NULL SELECT * FROM sc WHERE grade IS ‘ ’ SELECT * FROM sc WHERE grade IS NULL SELECT * FROM sc WHERE grade =‘ ’
SELECT * FROM sc WHERE grade=NULL SELECT * FROM sc WHERE grade IS ‘ ’ SELECT * FROM sc WHERE grade IS NULL SELECT * FROM sc WHERE grade =‘ ’
SELECT sno,cno FROM sc WHERE grade=NULL SELECT sno,cno FROM sc WHERE grade IS‘’ SELECT sno,cno FROM sc WHERE grade IS NULL SELECT sno,cno FROM sc WHERE grade=‘’
学生信息表s 学生信息表s和课程信息表c 学生信息表s、课程信息表c和学生选课信息表sc 学生信息表s和学生选课信息表sc
学生信息表s 学生信息表S和课程信息表c 学生信息表S、课程信息表c和学生选课信息表sc 学生信息表S和学生选课信息表sc
SELECT sno,cno FROM sc WHERE grade=NULL SELECT sno,cno FROM sc WHERE grade IS" SELECT sno,cno FROM sc WHERE grade IS NULL SELECT sno,cno FROM sc WHERE grade=''
SELECT * FROM sc WHERE grade=NULL SELECT * FROM sc WHERE grade IS" SELECT* FROM sc WHERE grade IS NULL SELECT* FROM sc WHERE grade="