Resource_Id                    Skills                 
------------------------------ -----------------------
Email1                         oracle,sqlserver,vb.net
Email2                         excel,java,sqlserver   
Email3                         java,oracle,vb.net     

declare @skills table (Resource_Id varchar(30),  Skill_Id varchar(20))
insert into @skills
select 'Email1' , 'sqlserver' union all
select 'Email1' , 'vb.net' union all
select 'Email1' , 'oracle' union all
select 'Email2', 'sqlserver' union all
select 'Email2', 'java' union all
select 'Email2', 'excel' union all
select 'Email3', 'vb.net' union all
select 'Email3', 'java' union all
select 'Email3', 'oracle'
---
select * from @skills s1
---  Concatenated Format
set statistics time on;
SELECT Resource_Id,stuff((    SELECT ',' + Skill_Id
                               FROM @skills s2
                             WHERE s2.Resource_Id= s1.resource_ID   --- must match GROUP BY below
                             ORDER BY Skill_Id
                               FOR XML PATH('')
                            ),1,1,'')  as [Skills]
FROM @skills s1
GROUP BY s1.Resource_Id --- without GROUP BY multiple rows are returned
ORDER BY s1.Resource_Id
set statistics time off;