如何将select出来的部分数据update到另一个表里面？

[amordp]

select distinct(name),count(name) num from t_col_desc group by name;

name num
a 1
b 2
c 3

select name,num from t_tbl_desc;

name num
a
b
c

以上是select出来的两张数据表，结构与字段都一样，都只有两个字段，name,num ,两张表name字段值相同， 其中一个表num字段没有值，将令一个表中的num字段中的值批量更新到没有值的字段中，怎么做？

[jinjazz]

update t_tbl_desc 
set num=b.name 
from t_tbl_desc  a ,
(
select name,count(name) num  from t_col_desc  group by name
)b
where a.name=b.name

[--小F--]

update 
  t_tbl_desc
set 
  num=b.num
from
  t_tbl_desc a,
  (select distinct(name) as name,count(name) num  from t_col_desc  group by name)b
where
   a.name=b.name

没必要发2遍

[amordp]

我用的oracle，没这样的语法-_-

[--小F--]

[Quote=引用 3 楼 amordp 的回复:]
我用的oracle，没这样的语法-_-
[/Quote]
建议去ORACLE问下

[jinjazz]

update t_tbl_desc a set num=(select count(name) from t_col_desc b where a.name=b.name)