return unique cate_id's, as a string separated by the specified separator ' '(space) in ascending order for each group of 'pub_id' from the book_mast table:

Publisher's IDGROUP_CONCAT(DISTINCT cate_id ORDER BY cate_id ASC SEPARATOR ' ')
P001CA002 CA004
P002CA003
P003CA001 CA003
P004CA002 CA005
P005CA001 CA004
P006CA001 CA005
P007CA002 CA005
P008CA004 CA005