select isnull(a.姓名,b.姓名) 姓名,a.成绩 as 5月成绩,b.成绩 as 3月成绩
from a full join b on a.姓名 = b.姓名

------解决方案--------------------
SQL code

select a.姓名,a.成绩 as 5月成绩,b.成绩 as 3月成绩
from a inner join b on a.姓名 = b.姓名

------解决方案--------------------
SQL code
select
 isnull(a.姓名,b.姓名) as  姓名,
 a.成绩 as '5月成绩',b.成绩 as '3月成绩'
from
 a full join b 
on
 a.姓名 = b.姓名

------解决方案--------------------
SELECT a.编号,a.姓名,a.成绩 AS [5月成绩],b.成绩 AS [3月成绩]
FROM A AS a JOIN B AS b ON a.编号=b.编号

------解决方案--------------------
探讨

SQL code
select
 isnull(a.姓名,b.姓名) as  姓名,
 a.成绩 as '5月成绩',b.成绩 as '3月成绩'
from
 a full join b 
on
 a.姓名 = b.姓名