sql中要这样查询该怎么写？？？急！！！！！！！！！！！！！！

[feeling_vb]

select count(*) from
(select 行业名称,媒体名称,一级编码 from aaa
group by 行业名称,媒体名称,一级编码)

这个查询语句不能执行 该怎么写！！！

[leeboyan]

这样呢？
select count(a.*) from
(select 行业名称,媒体名称,一级编码 from aaa
group by 行业名称,媒体名称,一级编码) a

[feeling_vb]

好像不行哦！！

[zheninchangjiang]

select count(*) from
(select 行业名称,媒体名称,一级编码 from aaa
group by 行业名称,媒体名称,一级编码) a

[yyc82]

select count(*) from
(select 行业名称,媒体名称,一级编码=min(一级编码) from aaa
group by 行业名称,媒体名称)

[progress99]

select count(*) from
(select distinct 行业名称,媒体名称,一级编码 from aaa
) a