数据库原理及应用实验指导★---实验4_SQL语言——SELECT查询操作(9)

实验4 SQL语言——SELECT查询操作

AND (G=90 OR G=80);

(3) SELECT S#,SN,SD FROM S

WHERE NOT EXISTS(SELECT * FROM C X WHERE NOT EXISTS

(SELECT * FROM SC Y WHERE Y.C#= X.C# AND Y.S#=S.S#));

(4) SELECT C#,CN FROM C WHERE C.C# NOT IN (SELECT SC.C# FROM SC);

(5) SELECT S#,COUNT(C#),AVG(G) FROM SC GROUP BY S# HAVING COUNT(C#)>3;

(6) DELETE FROM SC

WHERE SC.C# IN (SELECT C.C# FROM C WHERE CN='数据结构');

DELETE FROM C WHERE CN='数据结构';

9