从自定义子查询中选择列名称/别名列表

Question

在Oracle中，有没有一种方法可以选择从具有别名的自定义查询返回的所有列？举个例子，假设我们有一个查询，如下所示：

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

我想知道，如果封装查询可以进行，将返回：

COL1 
    COL2 
    COL3 

Answer 1

这里是如何做到这一点在PL/SQL中。不知道是否只有直接的oracle SQL才有可能。如有需要，您可以将其封装在某种功能中。

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;