在进行使用WM_CONCAT 进行列转行的字符串拼接时，可能会遇到长度超过4000的情况。这个时候oracle会报错。所以，在这个时候，最好的处理办法就是将结果集处理成CLOB格式。 下面是自定义的行转列函数。
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 ); 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; create or replace FUNCTION zh_concat(P1 VARCHAR2) RETURN clob AGGREGATE USING zh_concat_im ; 然后用自定义的ZH_CONCAT替换掉系统当中WM_CONCAT超长报错的地方，系统中直接将结果集映射成String型即可解决问题。
