单项选择题
A.SELECT Sno, COUNT(*) FROM SC GROUP BY Sno B.SELECT Sno FROM SC GROUP BY Sno WHERE COUNT(*)> 3 C.SELECT Sno FROM SC GROUP BY Sno HAVING COUNT(*)> 3 D.SELECT Sno FROM SC GROUP BY Sno
A.SUM(列名) B.MAX(列名) C.AVG(列名) D.COUNT(*)
A.左外连接 B.右外连接 C.内连接 D.自连接