select a.dept_code , a.costs, d.class_name
from a,
(select c.dept_code , b.class_name
from
(select distinct dept_code from b) c ,
b
where c.dept_code = b.dept_code)d
where a.dept_code = d.dept_code
from a,
(select c.dept_code , b.class_name
from
(select distinct dept_code from b) c ,
b
where c.dept_code = b.dept_code)d
where a.dept_code = d.dept_code
第二个问题:
update a set
dept_name =
(select b.dept_name FROM b where b.dept_code=a.dept_code)
对于第一个问题,我试过了,好像不行,但是受到启发,我改写为以下语句就可以了.
select a.dept_code , a.costs, d.class_name
from a,
(select dept_code , max( class_name) classname
from b group by dept_code) d
where a.dept_code = d.dept_code
受到启发,也是帮助,给分没商量.
第2个问题楼上这位朋友写的很对.给分.