oracle的聚集函数wm_concat()和listagg()不适用时，自定义通用的聚集函数合并查询结果列

    1.wm_concat()函数是oracle内部用户下的函数，通常不建议使用，而listagg()函数只在oracle11g下才有，这时候就需要自定义合并列的聚集函数，具体sql如下：

CREATE OR REPLACE TYPE T_LINK AS OBJECT(  STR VARCHAR2(32767),  STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT T_LINK) RETURN NUMBER,  MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF  IN OUT T_LINK,                                       VALUE IN VARCHAR2) RETURN NUMBER,  MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF        IN T_LINK,                                         RETURNVALUE OUT CLOB,                                         FLAGS       IN NUMBER)    RETURN NUMBER,  MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT T_LINK,                                     CTX2 IN T_LINK) RETURN NUMBER)/CREATE OR REPLACE TYPE BODY T_LINK IS  STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT T_LINK) RETURN NUMBER IS  BEGIN    SCTX := T_LINK(NULL);    RETURN ODCICONST.SUCCESS;  END;  MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF  IN OUT T_LINK,                                       VALUE IN VARCHAR2) RETURN NUMBER IS  BEGIN    SELF.STR := SELF.STR || VALUE || ',';    RETURN ODCICONST.SUCCESS;  END;  MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF        IN T_LINK,                                         RETURNVALUE OUT CLOB,                                         FLAGS       IN NUMBER) RETURN NUMBER IS  BEGIN    RETURNVALUE := SUBSTR(SELF.STR,                          1,                          LENGTH(SELF.STR) - 1);    RETURN ODCICONST.SUCCESS;  END;  MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT T_LINK,                                     CTX2 IN T_LINK) RETURN NUMBER IS  BEGIN    NULL;    RETURN ODCICONST.SUCCESS;  END;END;/CREATE OR REPLACE FUNCTION F_LINKS(P_STR VARCHAR2) RETURN CLOB  AGGREGATE USING T_LINK;/

把这段sql在oracle中运行一下，就可以使用了，具体使用示例如下：

select F_LINKS(t.name)  from PHY_DEVICE_TBL t where instr(c.deviceid, to_char(t.id)) > 0

合并的结果列之间是用逗号分隔的！