oracle高级SQL（四）--SQL行列转换专题2

--listagg方法  11g之后推荐使用这种
SELECT NO,
    listagg(EMP, ‘,‘) within GROUP (ORDER BY NULL) AS vals
FROM   onepiece
GROUP  BY NO ;
--wmsys.wm_concat方法 --11之前可使用这种
SELECT NO,
    WMSYS.WM_CONCAT(emp) AS vals
FROM   onepiece
GROUP  BY NO;
--使用集合函数；在用to_string函数将集合转换为字符串。需10g以上
SELECT NO,
    TO_STRING(CAST(COLLECT(emp) AS varchar2_ntt)) AS vals
FROM   onepiece
GROUP  BY NO; 

SELECT NO,
    listagg(EMP, ‘,‘) within GROUP (ORDER BY NULL) over (partition by no)
FROM   onepiece

CREATE OR REPLACE FUNCTION to_string
(
 nt_in        IN varchar2_ntt,
 delimiter_in IN VARCHAR2 DEFAULT ‘,‘
) RETURN VARCHAR2 IS
 v_idx PLS_INTEGER;
 v_str VARCHAR2(32767);
 v_dlm VARCHAR2(10);
BEGIN
 v_idx := nt_in.FIRST;
 WHILE v_idx IS NOT NULL
 LOOP
  v_str := v_str || v_dlm || nt_in(v_idx);
  v_dlm := delimiter_in;
  v_idx := nt_in.NEXT(v_idx);
 END LOOP;
 RETURN v_str;
END to_string;