两个数据库中相同表的对比sql语句怎么写

Answer 1

select
base.name, base.year
, a.成绩 as [a表成绩]
, b.成绩 as [b表成绩]
, case
when a.成绩 is null then 'a表中不存在'
when b.成绩 is null then 'b表中不存在'
when a.成绩=b.成绩 then '成功'
else '差异' end as 比较结果
from (
select name, year from tb_a
union
select name, year from tb_b
) as base
left join tb_a as a on a.name=base.name and a.year=base.year
left join tb_b as b on b.name=base.name and b.year=base.year