如何在SQL Server 2008中简化相关子查询？

Question

I have query in sql server which I want to simplify so that it can be Hive compatible. This is the query written in SQL format

SELECT session_id, 
       Substring ((SELECT ( ';' + tag_name ) 
               FROM   session_tag st2 
               WHERE  st2.session_id = st.session_id 
               FOR xml path ( '' )), 2, 1000) AS tags 
FROM   session_tag 
GROUP  BY session_id;

This is the result of this query

Once again I don't want to pass select query inside the substring function.

So I tried to simplify these query to get the same result the first query shows nothing and second one throws an error that subquery returned more than one result .

SELECT SUBSTRING(';'+tag_name,2,1000) as tag from session_tag st1 
where st1.session_id = (select st2.session_id from session_tag st2 where st1.session_id = st2.session_id for xml path (''))

and

SELECT SUBSTRING(';'+tag_name,2,1000) as tag from session_tag st1 
where st1.session_id = (select st2.session_id from session_tag st2 where st1.session_id = st2.session_id) for xml path('')

Answer 1

Finally I got the solution. The simplified version of this query is

SELECT session_id, Substring(d.tagList,2,1000) as tag from (
select distinct session_id from session_tag) a
cross apply 
(
    select ';'+tag_name from session_tag as b
    where a.session_id = b.session_id for xml path ('')
) d (tagList)