-選擇列表中的列 'Student.sname' 無(wú)效，因?yàn)樵摿袥]有包含在聚合函數(shù)或 GROUP BY 子句中。 
SELECT Student.sno,sname,AVG(grade) AS avg_g 
FROM Student,SC  www.jb51.net 
WHERE Student.sno=SC.sno AND cno>'008' 
GROUP BY Student.sno --沒加 Student. 列名 'sno' 不明確。 
HAVING MIN(grade) >= 60 
ORDER BY avg_g DESC; 

/* 
把對(duì)Student表和Course表的全部權(quán)限授予用戶U2和U3  
 GRANT ALL PRIVILIGES www.jb51.net   
        ON TABLE Student, Course  
           TO U2, U3;  
把對(duì)表SC的查詢權(quán)限授予所有用戶  
GRANT SELECT ON TABLE SC  
TO PUBLIC; 
把查詢Student表和修改學(xué)生學(xué)號(hào)的權(quán)限授給用戶U4  
GRANT UPDATE(Sno), SELECT  
           ON TABLE Student TO U4; 
把用戶U4修改學(xué)生學(xué)號(hào)的權(quán)限收回  
 REVOKE UPDATE(Sno) ON TABLE Student FROM U4; 
*/