select a.学号 , a.姓名 , b.课程名
from tbStudent a , tbCourse b , tbScore c
where c.成绩 < 60 and a.学号 = c.学号 and b.课程号 = c.课程号
select b.学号,b.姓名,c.课程名
from tbScore as a inner join tbStudent as b on a.学号=b.学号
inner join tbCourse as c on a.课程号=c.课程号
where a.成绩<60