SQL> create table a(col varchar2(3));
SQL> insert into a select '春' from dual;
SQL> insert into a select '夏' from dual;
SQL> insert into a select '秋' from dual;
SQL> insert into a select '冬' from dual;
SQL> select regexp_substr(wm_concat(col),'[^,]+') col1,
  2      regexp_substr(wm_concat(col),'[^,]+[,]+[^,]+') col2,
  3      regexp_substr(wm_concat(col),'[^,]+[,]+[^,]+[,]+[^,]+') col3,
  4      wm_concat(col) col4 from a;

COL1       COL2       COL3       COL4                                           
---------- ---------- ---------- ---------------                                
春         春,夏      春,夏,秋   春,夏,秋,冬

------解决方案--------------------
SQL code
select max(decode(rn, 1, col)) col1,
       max(decode(rn, 2, col)) col2,
       max(decode(rn, 3, col)) col3,
       max(decode(rn, 4, col)) col4 from (
select wm_concat(col) over (order by rownum) col, rownum rn from a);