oracle - 从自定义子查询中选择列名称/别名列表

Question

在 Oracle 中，有没有办法选择带有别名的自定义查询返回的所有列？举个例子，假设我们有一个如下查询:

    SELECT FIRST_NAME AS COL1, LAST_NAME AS COL2, ADDRESS AS COL3
    FROM PEOPLE

我想知道是否可以进行封装查询并返回:

    COL1
    COL2
    COL3

Answer 1

以下是如何在 PL/SQL 中执行此操作。不知道是否可以仅使用直接的 oracle SQL。如果需要，您始终可以将其封装在某种函数中。

DECLARE
   TYPE RefCursor_Type IS REF CURSOR;

   D_RefCur             RefCursor_Type;
   D_DescriptionTable   DBMS_SQL.DESC_TAB2;
   D_ColumnCount        INTEGER;
   D_CursorHandle       INTEGER;
BEGIN
   OPEN D_RefCur
   FOR 'SELECT FIRST_NAME AS COL1, LAST_NAME AS COL2, ADDRESS AS COL3 FROM PEOPLE';

   D_CursorHandle := DBMS_SQL.to_cursor_number (D_RefCur);

   DBMS_SQL.DESCRIBE_COLUMNS2 (D_CursorHandle,
                               D_ColumnCount,
                               D_DescriptionTable);


   FOR idx IN 1 .. D_ColumnCount
   LOOP
      DBMS_OUTPUT.put_line (D_DescriptionTable (idx).col_name);
   END LOOP;
END;