ORACLE管道化表函数

        table型函数用来返回类似表结构的集合，常规的table型函数需要先填充完集合才能返回，如果集合对象太大会消耗大量内存；pipelined的table型函数能够在边填充时边返回，从而避免占用过多内存。

一.Table Functions

-- Create the types to support the table function.
DROP TYPE t_tf_tab;
DROP TYPE t_tf_row;

CREATE TYPE t_tf_row AS OBJECT (
  id           NUMBER,
  description  VARCHAR2(50)
);
/

CREATE TYPE t_tf_tab IS TABLE OF t_tf_row;
/

-- Build the table function itself.
CREATE OR REPLACE FUNCTION get_tab_tf (p_rows IN NUMBER) RETURN t_tf_tab AS
  l_tab  t_tf_tab := t_tf_tab();
BEGIN
  FOR i IN 1 .. p_rows LOOP
    l_tab.extend;
    l_tab(l_tab.last) := t_tf_row(i, 'Description for ' || i);
  END LOOP;

  RETURN l_tab;
END;
/

运行如下语句测试一下

-- Test it.
SELECT *
FROM   TABLE(get_tab_tf(10))
ORDER BY id DESC;

结果如下：

二.Pipelined Table Functions

-- Build a pipelined table function.
CREATE OR REPLACE FUNCTION get_tab_ptf (p_rows IN NUMBER) RETURN t_tf_tab PIPELINED AS
BEGIN
  FOR i IN 1 .. p_rows LOOP
    PIPE ROW(t_tf_row(i, 'Description for ' || i));   
  END LOOP;

  RETURN;
END;
/

运行如下语句测试一下

-- Test it.
SELECT *
FROM   TABLE(get_tab_ptf(10))
ORDER BY id DESC;

结果如下：

文章来源：http://blog.csdn.net/t0nsha/article/details/7479385