Need help in creating a query I have a table with below data.

columnA  columnB
ONE      value 1
ONE      value 2
ONE      value 3
TWO      value 1
TWO      value 2
THREE    value 1


Need help in creating a query which gives below

COLUMN X   COLUMN Y
ONE         value 1, value 2, value 3
TWO         value 1, value 2
THREE       value 1
What you are needing help is called Grouped Concatenation in SQL Server

This sql fiddle that I created will help you. 

Basically you use stuff + FOR XML PATH.

If you are on sql server 2017 (vNEXT) then STRING_AGG is an inbuilt function that you can use

-- sql server vNEXT 

SELECT [ColumnA]  =  [ColumnA],
       [ColumnBs] = STRING_AGG(ColumnB, ',')
 from dbo.Table1   
 group by ColumnA