Ｏｒａｃｌｅ自定义聚集函数

-- 创建对象类型

CREATE OR REPLACE TYPE T_LINK AS OBJECT (
STR VARCHAR2(30000),
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 VARCHAR2,FLAGS IN NUMBER) RETURN NUMBER,
MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT T_LINK,CTX2 IN T_LINK) RETURN NUMBER
)
/

-- 建立包体

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
SCTX.STR := SELF.STR || VALUE;
RETURN ODCICONST.SUCCESS;
END;
MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN T_LINK, RETURNVALUE OUT VARCHAR2, FLAGS IN NUMBE
R) RETURN NUMBER IS
BEGIN
RETURNVALUE :=SELF.STR;
RETURN ODCICONST.SUCESS;
END;
END;

/

-- 创建函数

CREATE OR REPLACE FUNCTION F_LINK(P_STR VARCHAR2) RETURN VARCHAR2

AGGREGATE USING T_LINK;

/

-- 建表

CREATE TABLE TEST (ID NUMBER, NAME VARCHAR2(20));

-- 使用F_LINK

SELECT ID, F_LINK(NAME) NAME FROM TEST GROUP BY ID;