oracle管道化表函數

在實際的應用中，爲了讓PL/SQL 函數返回數據的多個行，必須通過返回一個 REF CURSOR 或一個數據集合來完成。REF CURSOR 的這種情況侷限於可以從查詢中選擇的數據，而整個集合在可以返回前，必須進行具體化。 9i 通過引入的管道化表函數糾正了後一種情況。表函數是返回整個行的集（通常作爲一個集合）的函數，可以直接從 SQL 語句中進行查詢，就好像它是一個真正的數據庫表一樣。管道化表函數與之相似，但是它像在構建時一樣返回數據，而不是一次全部返回。管道化表函數更加有效，因爲數據可以儘可能快地返回。

    管道化表函數必須返回一個集合。在函數中，PIPE ROW 語句被用來返回該集合的單個元素，該函數必須以一個空的 RETURN 語句結束，以表明它已經完成。一旦我們創建了上述函數，我們就可以使用 TABLE 操作符從 SQL 查詢中調用它。

例1：
Type Definition

CREATE OR REPLACE TYPE COLOR_HEX_CODE AS OBJECT
(
  -- Attributes
  colorName Varchar2(10),
  colorCode varchar2(10)

  -- Member functions and procedures
  --member procedure <ProcedureName>(<Parameter> <Datatype>)
);

CREATE OR REPLACE TYPE COLOR_HEX_CODE AS OBJECT
(
  -- Attributes
  colorName Varchar2(10),
  colorCode varchar2(10)
  
  -- Member functions and procedures
  --member procedure <ProcedureName>(<Parameter> <Datatype>)
);

Create Table Type

CREATE OR REPLACE TYPE COLOR_TYPE AS TABLE OF COLOR_HEX_CODE;

CREATE OR REPLACE TYPE COLOR_TYPE AS TABLE OF COLOR_HEX_CODE;

Create Table Function

CREATE OR REPLACE FUNCTION F_PIPELINE_TEST RETURN COLOR_TYPE PIPELINED
AS
BEGIN
    PIPE ROW(COLOR_HEX_CODE('black','#000000'));
    PIPE ROW(COLOR_HEX_CODE('white','#FFFFFF'));
    PIPE ROW(COLOR_HEX_CODE('red','#FF0000'));
    PIPE ROW(COLOR_HEX_CODE('green','#00FF00'));
    PIPE ROW(COLOR_HEX_CODE('blue','#0000FF'));
    RETURN;
END;

CREATE OR REPLACE FUNCTION F_PIPELINE_TEST RETURN COLOR_TYPE PIPELINED
AS
BEGIN
    PIPE ROW(COLOR_HEX_CODE('black','#000000'));
    PIPE ROW(COLOR_HEX_CODE('white','#FFFFFF'));
    PIPE ROW(COLOR_HEX_CODE('red','#FF0000'));
    PIPE ROW(COLOR_HEX_CODE('green','#00FF00'));
    PIPE ROW(COLOR_HEX_CODE('blue','#0000FF'));
    RETURN;
END;

測試:

select * from table( f_pipeline_test );

select * from table( f_pipeline_test );

結果：
COLORNAME  COLORCODE
black   #000000
white   #FFFFFF
red   #FF0000
green   #00FF00
blue   #0000FF

例2：實現split函數功能

CREATE OR REPLACE TYPE RESOLVE_STR IS TABLE OF VARCHAR2 (4000);

CREATE OR REPLACE TYPE RESOLVE_STR IS TABLE OF VARCHAR2 (4000);

 

CREATE OR REPLACE FUNCTION F_SPLIT
    (
       P_STR       IN   VARCHAR2,
       P_DELIMITER IN   varchar2
     ) RETURN RESOLVE_STR PIPELINED
AS
    j     INT := 0;
    i     INT := 1;
    len   INT := 0;
    len1  INT := 0;
    tmp   VARCHAR2 (4000);
    v_str VARCHAR2 (4000);
BEGIN
    v_str := TRIM(BOTH P_DELIMITER FROM P_STR);--去掉前後的分隔符
    len := LENGTH (v_str);
    len1 := LENGTH(P_DELIMITER);

    WHILE j < len
      LOOP
          j := INSTR (v_str, P_DELIMITER, i);--尋分隔符位置

          IF j = 0 THEN--沒有了
              tmp := SUBSTR (v_str, i);
              PIPE ROW (tmp);
              EXIT;--結束
          ELSE
              tmp := SUBSTR (v_str, i, j - i);
              i := j + len1;
              PIPE ROW (tmp);
          END IF;
      END LOOP;

    RETURN;
END;

CREATE OR REPLACE FUNCTION F_SPLIT
    (
       P_STR       IN   VARCHAR2,
       P_DELIMITER IN   varchar2
     ) RETURN RESOLVE_STR PIPELINED
AS
    j     INT := 0;
    i     INT := 1;
    len   INT := 0;
    len1  INT := 0;
    tmp   VARCHAR2 (4000);
    v_str VARCHAR2 (4000);
BEGIN
    v_str := TRIM(BOTH P_DELIMITER FROM P_STR);--去掉前後的分隔符
    len := LENGTH (v_str);
    len1 := LENGTH(P_DELIMITER);

    WHILE j < len
      LOOP
          j := INSTR (v_str, P_DELIMITER, i);--尋分隔符位置

          IF j = 0 THEN--沒有了
              tmp := SUBSTR (v_str, i);
              PIPE ROW (tmp);
              EXIT;--結束
          ELSE
              tmp := SUBSTR (v_str, i, j - i);
              i := j + len1;
              PIPE ROW (tmp);
          END IF;
      END LOOP;

    RETURN;
END;

測試：

SELECT * FROM TABLE (F_SPLIT('-12-02-ab-cd-a0-ef-', '-'));

SELECT * FROM TABLE (F_SPLIT('-12-02-ab-cd-a0-ef-', '-'));

例3：產生6個0..49的隨機數
First the quick-and-dirty solution without a pipelined function

select r from (
       select r from (
              select rownum r from all_objects where rownum < 50
                     ) order by dbms_random.VALUE
              )where rownum <= 6;

select r from (
       select r from (
              select rownum r from all_objects where rownum < 50
                     ) order by dbms_random.VALUE
              )where rownum <= 6;

pipelined function

CREATE OR REPLACE TYPE ARRAY AS TABLE OF NUMBER;

CREATE OR REPLACE TYPE ARRAY AS TABLE OF NUMBER;

 

CREATE OR REPLACE FUNCTION gen_numbers(n IN NUMBER DEFAULT NULL)
RETURN ARRAY PIPELINED
AS
  BEGIN
    FOR i IN 1 .. nvl(n,9999)
    LOOP
    PIPE ROW(i);
    END LOOP;
  RETURN;
END;

CREATE OR REPLACE FUNCTION gen_numbers(n IN NUMBER DEFAULT NULL)
RETURN ARRAY PIPELINED
AS
  BEGIN
    FOR i IN 1 .. nvl(n,9999)
    LOOP
    PIPE ROW(i);
    END LOOP;
  RETURN;
END;

測試：

select * from (
  select *
    from (select * from table(gen_numbers(49)))  order by dbms_random.random
  )
where rownum <= 6

select * from (
  select *
    from (select * from table(gen_numbers(49)))  order by dbms_random.random
  )
where rownum <= 6

generating that range of dates

select to_date('2009-5-10','yyyy-mm-dd') + column_value-1 from TABLE(gen_numbers(15));

select to_date('2009-5-10','yyyy-mm-dd') + column_value-1 from TABLE(gen_numbers(15));

Note the name of the column we used: COLUMN_VALUE. That is the default name for the column coming back from the PIPELINED function.
another example

CREATE OR REPLACE TYPE date_array AS TABLE OF DATE;

CREATE OR REPLACE TYPE date_array AS TABLE OF DATE;

 

CREATE OR REPLACE FUNCTION date_table(sdate DATE, edate DATE)
RETURN date_array PIPELINED AS
BEGIN
  FOR i IN 0 .. (edate - sdate)
  LOOP
    PIPE ROW(sdate + i);
  END LOOP;
  RETURN;
END date_table;