将多行数据拼接成一行：

--wmsys.wm_concatselect wmsys.wm_concat(a.hdid) as test from flow_currentrecord a where a.flowid=222 group by a.flowid;

但有大小限制：字符串缓冲区太小，超过varchar 4000长度。

扩展：更改返回类型为clob

--Type CREATE OR REPLACE TYPE zh_concat_im AUTHID CURRENT_USER AS OBJECT (   CURR_STR clob,   STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT zh_concat_im)     RETURN NUMBER,   MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT zh_concat_im,                                        P1   IN VARCHAR2) RETURN NUMBER,   MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF        IN zh_concat_im,                                          RETURNVALUE OUT clob,                                          FLAGS       IN NUMBER)     RETURN NUMBER,   MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF  IN OUT zh_concat_im,                                      SCTX2 IN zh_concat_im) RETURN NUMBER ); / --TYPE BODY CREATE OR REPLACE TYPE BODY zh_concat_im IS  STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT zh_concat_im)     RETURN NUMBER IS  BEGIN    SCTX := zh_concat_im(NULL);     RETURN ODCICONST.SUCCESS;   END;   MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT zh_concat_im,                                        P1   IN VARCHAR2) RETURN NUMBER IS  BEGIN    IF (CURR_STR IS NOT NULL) THEN      CURR_STR := CURR_STR || ',' || P1;     ELSE      CURR_STR := P1;     END IF;     RETURN ODCICONST.SUCCESS;   END;   MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF        IN zh_concat_im,                                          RETURNVALUE OUT clob,                                          FLAGS       IN NUMBER) RETURN NUMBER IS  BEGIN    RETURNVALUE := CURR_STR;     RETURN ODCICONST.SUCCESS;   END;   MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF  IN OUT zh_concat_im,                                      SCTX2 IN zh_concat_im) RETURN NUMBER IS  BEGIN    IF (SCTX2.CURR_STR IS NOT NULL) THEN      SELF.CURR_STR := SELF.CURR_STR || ',' || SCTX2.CURR_STR;     END IF;     RETURN ODCICONST.SUCCESS;   END; END;  / --FUNCTION  create or replace FUNCTION zh_concat(P1 VARCHAR2) RETURN clob AGGREGATE USING zh_concat_im;

调用：

select zh_concat(a.hdid) as test from flow_currentrecord a where a.flowid=222 group by a.flowid;