Product_Id      Description
  BX01              Desc 1
  BxX1              Desc 2
  Dss3              Desc 3
  HHXY              Desc 4

DECLARE @ProID VARCHAR(8000)
SELECT @ProID = COALESCE(@ProID + ' - ', '') + Product_Id FROM TABLE
SELECT @ProID

SELECT GROUP_CONCAT(
            CONCAT( @rownum := @rownum + 1, '-', Product_Id )
            SEPARATOR ','
       ) AS data
FROM table, ( select @rownum := 0 ) r

SET @a:=0;

SELECT CONCAT( @a:=@a+1,'-',Product_Id) FROM TABLE ;