行转列、列转行（sys_connect_by_path，row_number() over，count(*) over）,wmsys.wm_concat

SYS_CONNECT_BY_PATH这个函数是oracle9i才新提出来的！

它一定要和connect by子句合用！

第一个参数是形成树形式的字段，第二个参数是父级和其子级分隔显示用的分隔符！

START WITH 代表你要开始遍历的的节点
CONNECT BY PRIOR 是标示父子关系的对应

select deptno,
ltrim(sys_connect_by_path(ename,','),',') emps
from (
select deptno,
ename,
row_number() over
(partition by deptno order by empno) rn,
count(*) over
(partition by deptno) cnt
from emp
)
where level = cnt
start with rn = 1
connect by prior deptno = deptno and prior rn = rn-1;

   DEPTNO EMPS
----------------------------------------------
       10 CLARK,KING,MILLER
       20 SMITH,JONES,SCOTT,ADAMS,FORD
       30 ALLEN,WARD,MARTIN,BLAKE,TURNER,JAMES

SQL> select deptno,wmsys.wm_concat(ename) from emp group by deptno;

DEPTNO WMSYS.WM_CONCAT(ENAME)
---------- --------------------------------------------------------------------------------
10 CLARK,MILLER,KING
20 SMITH,FORD,ADAMS,SCOTT,JONES
30 ALLEN,JAMES,TURNER,BLAKE,MARTIN,WARD

select deptno,
ename,
row_number() over
(partition by deptno order by empno) rn,
count(*) over
(partition by deptno) cnt
from emp;

DEPTNO ENAME              RN        CNT
---------- ---------- ---------- ----------
10 CLARK               1          3
10 KING                2          3
10 MILLER              3          3
20 SMITH               1          5
20 JONES               2          5
20 SCOTT               3          5
20 ADAMS               4          5
20 FORD                5          5
30 ALLEN               1          6
30 WARD                2          6
30 MARTIN              3          6
30 BLAKE               4          6
30 TURNER              5          6
30 JAMES               6          6

SQL> select ','||'7654,7698,7782,7788'||',' emps from dual;

EMPS
---------------------
,7654,7698,7782,7788,

select substr(emps,instr(emps,',',1,iter.pos)+1,4)   from (select ','||'7654,7698,7782,7788'||',' emps
from dual) csv,
(select rownum pos from emp) iter
where iter.pos <=
((length(csv.emps)-length(replace(csv.emps,',')))/length(','))-1;

SUBSTR(E
--------
7654
7698
7782
7788

select substr(emps, instr(emps, ',', 1, 1) + 1, 4),
substr(emps, instr(emps, ',', 1, 2) + 1, 4),
substr(emps, instr(emps, ',', 1, 3) + 1, 4),
substr(emps, instr(emps, ',', 1, 4) + 1, 4)
from (select ',' || '7654,7698,7782,7788' || ',' emps from dual) csv;

SUBS SUBS SUBS SUBS
---- ---- ---- ----
7654 7698 7782 7788