select xm_id,xk1||','||xk2||','||xk3 xk from t_xm;
select xm_id,xk1 from t_xm union all select xm_id,xk2 from t_xm union all select xm_id,xk3 from t_xm
select t1.xm_id,t1.xk1 xk from t_xm t1 union all select t2.xm_id,t2.xk2 xk from t_xm t2 union all select t3.xm_id,t3.xk3 xk from t_xm t3 order by xm_id;
union all
select xm_id,xk2 from t_xm
union all
select xm_id,xk3 from t_xm
union all
select t2.xm_id,t2.xk2 xk from t_xm t2
union all
select t3.xm_id,t3.xk3 xk from t_xm t3
order by xm_id;