在Oracle中，wm_concat()函數用于將多行數據合并為一個字符串

1. 使用LISTAGG()函數：

SELECT LISTAGG(column_name, ',') WITHIN GROUP (ORDER BY column_order) AS concatenated_string
FROM table_name;

2. 使用COLLECT()和CAST()函數：

SELECT CAST(COLLECT(column_name ORDER BY column_order) AS string_table_type) AS concatenated_string
FROM table_name;

這里，string_table_type是一個自定義的字符串表類型。首先需要創建一個類型：

CREATE TYPE string_table_type AS TABLE OF VARCHAR2(4000);

3. 使用自定義聚合函數：

創建一個自定義聚合函數，例如my_concat()，然后使用它來合并多行數據：

SELECT my_concat(column_name) AS concatenated_string
FROM table_name;

創建自定義聚合函數的示例代碼：

CREATE OR REPLACE TYPE my_concat_impl AS OBJECT (
  concatenated_string VARCHAR2(32767),

  STATIC FUNCTION ODCIAggregateInitialize(sctx IN OUT my_concat_impl) RETURN NUMBER,
  MEMBER FUNCTION ODCIAggregateIterate(self IN OUT my_concat_impl, value IN VARCHAR2) RETURN NUMBER,
  MEMBER FUNCTION ODCIAggregateTerminate(self IN my_concat_impl, returnValue OUT VARCHAR2, flags IN NUMBER) RETURN NUMBER,
  MEMBER FUNCTION ODCIAggregateMerge(self IN OUT my_concat_impl, ctx2 IN my_concat_impl) RETURN NUMBER
);
/

CREATE OR REPLACE TYPE BODY my_concat_impl IS
  STATIC FUNCTION ODCIAggregateInitialize(sctx IN OUT my_concat_impl) RETURN NUMBER IS
  BEGIN
    sctx := my_concat_impl(NULL);
    RETURN ODCIConst.Success;
  END;

  MEMBER FUNCTION ODCIAggregateIterate(self IN OUT my_concat_impl, value IN VARCHAR2) RETURN NUMBER IS
  BEGIN
    IF self.concatenated_string IS NULL THEN
      self.concatenated_string := value;
    ELSE
      self.concatenated_string := self.concatenated_string || ',' || value;
    END IF;
    RETURN ODCIConst.Success;
  END;

  MEMBER FUNCTION ODCIAggregateTerminate(self IN my_concat_impl, returnValue OUT VARCHAR2, flags IN NUMBER) RETURN NUMBER IS
  BEGIN
    returnValue := self.concatenated_string;
    RETURN ODCIConst.Success;
  END;

  MEMBER FUNCTION ODCIAggregateMerge(self IN OUT my_concat_impl, ctx2 IN my_concat_impl) RETURN NUMBER IS
  BEGIN
    IF self.concatenated_string IS NULL THEN
      self.concatenated_string := ctx2.concatenated_string;
    ELSIF ctx2.concatenated_string IS NOT NULL THEN
      self.concatenated_string := self.concatenated_string || ',' || ctx2.concatenated_string;
    END IF;
    RETURN ODCIConst.Success;
  END;
END;
/

CREATE FUNCTION my_concat(input VARCHAR2) RETURN VARCHAR2 PARALLEL_ENABLE AGGREGATE USING my_concat_impl;
/

以上三種替代方案都可以實現類似于wm_concat()函數的功能，將多行數據合并為一個字符串。根據實際情況和需求選擇合適的方法。