A
SELECT s.sno,sname, grade FROM student s ,score sc WHERE s.sno=sc.sno AND s.smajor='信息管理' AND cname='DB' ;
B
SELECT s.sno,sname, grade FROM student s,score sc WHERE s.smajor='信息管理' AND cname='DB';
C
SELECT s.sno,sname, grade FROM student s WHERE smajor='信息管理' AND cname='DB';
D
SELECT s.sno,sname, grade FROM student s WHERE s.sno=sc.sno AND s.smajor='信息管理' AND cname='DB';
