Comma separated values from sql table :

--Create temp table & Insert data-----
Create table #temp(id int, tech nvarchar(10))
Insert into #temp(id,tech) values(12, 'c#'),(12,'java'),(13,'sql'),(13,'Oracle'),(13,'Mysql'),(15,'hadoop')
Select * from #temp
--------------------------------------
--Process data------------------------
;WITH cte AS
(
SELECT DISTINCT id 
FROM #temp
)
SELECT Id, STUFF((SELECT ', ' + CAST(t2.tech AS NVARCHAR(MAX))
     FROM #temp t2 WHERE t1.ID = t2.ID
     FOR XML PATH('')),1,1,'') skills
into #temp1
FROM cte t1
--Getting Result---------------------
Select * from #temp1
--Drop temp tables-------------------
Drop table #temp
Drop table #temp1
-------------------------------------