有结果集A
id name grade
1 zhanglin null
2 wangtao 80
3 zhaobin null有结果集B
id name grade
1 zhanglin 88
2 wangtao null
3 zhaobin null希望这样查询select A.id,a.name,case when A.grade IS null then B.grade else A.grade end
得到如下记录
1 zhanglin 88 (from B)
2 wangtao 80 (from A)
3 zhaobin null (from B)
id name grade
1 zhanglin null
2 wangtao 80
3 zhaobin null有结果集B
id name grade
1 zhanglin 88
2 wangtao null
3 zhaobin null希望这样查询select A.id,a.name,case when A.grade IS null then B.grade else A.grade end
得到如下记录
1 zhanglin 88 (from B)
2 wangtao 80 (from A)
3 zhaobin null (from B)
from a,b
where a.id=b.id
from a inner join b on a.id=b.id
or
select a.id,a.name,case when A.grade IS null then B.grade else A.grade end
from a inner join b on a.id=b.id
from a inner join b on a.id=b.id