--Start by making some test data
DECLARE @TABLE AS TABLE(
[RequestID] INT,
[ApprovalName] VARCHAR(35))

INSERT INTO @TABLE([RequestID],[ApprovalName])
SELECT 15, 'Manager'
UNION ALL SELECT 15, 'Director'
UNION ALL SELECT 16, 'Manager'
UNION ALL SELECT 16, 'Director'
UNION ALL SELECT 16, 'Procurement Head'

--Now to the query
;WITH cte ( [RequestID], [Approval List], [ApprovalName], length )
     AS (SELECT [RequestID],
                CAST('' AS VARCHAR(8000)),
                CAST('' AS VARCHAR(8000)),
                0
         FROM   @TABLE
         GROUP  BY [RequestID]
         UNION ALL
         SELECT p.[RequestID],
                CAST([Approval List] + CASE
                                         WHEN length = 0 THEN ''
                                         ELSE ', '
                                       END + p.[ApprovalName] AS VARCHAR(8000)),
                CAST(p.[ApprovalName] AS VARCHAR(8000)),
                length + 1
         FROM   cte c
                INNER JOIN @TABLE p
                  ON c.[RequestID] = p.[RequestID]
         WHERE  p.[ApprovalName] > c.[ApprovalName])
SELECT [RequestID],
       [Approval List]
FROM   (SELECT [RequestID],
               [Approval List],
               Rank() OVER ( PARTITION BY [RequestID] ORDER BY length DESC )
        FROM   cte) d ( [RequestID], [Approval List], rank )
WHERE  rank = 1 

/*
RequestID   Approval List
----------- -------------------------------------
15          Director, Manager
16          Director, Manager, Procurement Head
*/

declare @skills table (Resource_Id int,  Skill_Id varchar(20))
insert into @skills
select 101, 'sqlserver' union all
select 101, 'vb.net' union all
select 101, 'oracle' union all
select 102, 'sqlserver' union all
select 102, 'java' union all
select 102, 'excel' union all
select 103, 'vb.net' union all
select 103, 'java' union all
select 103, '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;