将多行数据拼接成一行：
--wmsys.wm_concat
select 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;