update a
set 借书册数=b.con
from 读者 a
join
(select count(书号) as con,读者编号 from 借阅 group by 读者编号)b on a.编号=b.读者编号
set 借书册数=b.con
from 读者 a
join
(select count(书号) as con,读者编号 from 借阅 group by 读者编号)b on a.编号=b.读者编号
调试欢乐多
我觉得这个字段写个 触发器比较好 ,而不是人工去更改