WM_CONCAT函数（Oracle）

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本文介绍了一种在Oracle数据库中使用自定义类型WM_CONCAT_IMPL实现字符串聚合的方法。通过创建并替换类型WM_CONCAT_IMPL，定义了四个成员函数以实现字符串的初始化、迭代、终止和合并操作。最后，通过一个聚合函数wm_concat展示了如何使用该类型来完成字符串的拼接。

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CREATE OR REPLACE TYPE WM_CONCAT_IMPL AS OBJECT
-- AUTHID CURRENT_USER AS OBJECT
(
CURR_STR VARCHAR2(32767),
STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT WM_CONCAT_IMPL)
RETURN NUMBER,
MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT WM_CONCAT_IMPL,
P1 IN VARCHAR2) RETURN NUMBER,
MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN WM_CONCAT_IMPL,
RETURNVALUE OUT VARCHAR2,
FLAGS IN NUMBER)
RETURN NUMBER,
MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT WM_CONCAT_IMPL,
SCTX2 IN WM_CONCAT_IMPL) RETURN NUMBER
);
/

CREATE OR REPLACE TYPE BODY WM_CONCAT_IMPL IS
STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT WM_CONCAT_IMPL)
RETURN NUMBER IS
BEGIN
SCTX := WM_CONCAT_IMPL(NULL);
RETURN ODCICONST.SUCCESS;
END;
MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT WM_CONCAT_IMPL,
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 WM_CONCAT_IMPL,
RETURNVALUE OUT VARCHAR2,
FLAGS IN NUMBER) RETURN NUMBER IS
BEGIN
RETURNVALUE := CURR_STR;
RETURN ODCICONST.SUCCESS;
END;
MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT WM_CONCAT_IMPL,
SCTX2 IN WM_CONCAT_IMPL) 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 wm_concat(P1 VARCHAR2) RETURN VARCHAR2
AGGREGATE USING WM_CONCAT_IMPL;