下列选项中哪一个是正确的空值查询条件的SQL表达（）

B.AGEISNOTNULL

C.AGE=NULL

D.NOT(AGEISNULL)

B.scoreisnotNull

C.score=Null

D.NOT(scoreISNULL)

A．AGE IS NULL  B．AGE IS NOT NULL

C．AGE=NULL D．NOT(AGE IS NULL)

A、以“HUST_DB”为首的字符串

B、以“HUST_”为首，“DB_”为尾的字符串

C、以“HUST_”为首，“DB”为尾部倒数第3、第2个字符的字符串

D、以上选项都不正确

A、SELECT Sno, AVG(Grade) FROM SC GROUP BY Sno HAVING AVG(Grade)>=60;

B、SELECT Sno FROM SC WHERE Grade>=60 GROUP BY Sno;

C、SELECT Sno, Grade FROM SC GROUP BY Sno HAVING AVG(Grade)>=60;

D、SELECT Sno FROM SC GROUP BY Sno HAVING Grade >=60;

A、ORDER BY GRADE, SNO

B、ORDER BY GRADE DESC, SNO

C、ORDER BY GRADE DESC

D、ORDER BY SNO ASC, GRADE DESC

A、100

B、10

C、1000

D、不确定

A、SELECT

B、WHERE

C、HAVING

D、ORDER BY

A、=ALL

B、=ANY

C、EXISTS

D、EXCEPT