Oracle 中 table 函数的应用

        表函数可接受查询语句或游标作为输入参数，并可输出多行数据。该函数可以平行执行，并可持续输出数据流，被称作管道式输出。应用表函数可将数据转换分阶段处理，并省去中间结果的存储和缓冲表。

 

1. 用游标传递数据
利用游标 REF CURSOR 可将数据集（多行记录）传递到PL/SQL函数：
SELECT *
  FROM TABLE (myfunction (CURSOR (SELECT *
                                    FROM mytab)));
                                    
2. 利用两个实体化视图（或表）作为样板数据
CREATE MATERIALIZED VIEW sum_sales_country_mv
BUILD IMMEDIATE
REFRESH COMPLETE
ENABLE QUERY REWRITE
AS
SELECT   SUBSTR (s.calendar_month_desc, 1, 4) YEAR, c.country_id country,
         SUM (sum_amount_sold) sum_amount_sold
    FROM sum_sales_month_mv s, customers c
   WHERE s.cust_id = c.cust_id
     AND c.country_id IN ('US', 'UK', 'FR', 'ES', 'JP', 'AU')
GROUP BY SUBSTR (s.calendar_month_desc, 1, 4), c.country_id;

 

CREATE MATERIALIZED VIEW sum_es_gend_mv
BUILD DEFERRED
REFRESH FAST
ENABLE QUERY REWRITE
AS
SELECT   SUBSTR (s.calendar_month_desc, 1, 4) YEAR,
         s.calendar_month_desc cal_month, c.cust_gender,
         SUM (sum_amount_sold) sum_amount_sold
    FROM sum_sales_month_mv s, customer c
   WHERE s.cust_id = c.cust_id
     AND c.country_id = 'ES'
     AND sunstr (s.calendar_month_desc, 1, 4) = '2000'
GROUP BY SUBSTR (s.calendar_month_desc, 1, 4),
         s.calendar_month_desc,
         c.cust_gender;
         
3. 定义对象类型和基于对象类型的表类型
定义对象类型并且为进一步引用做好准备。
（1）定义对象类型：TYPE sales_country_t
CREATE TYPE sales_country_t AS OBJECT (
   YEAR              VARCHAR2 (4),
   country           CHAR (2),
   sum_amount_sold   NUMBER
);
（2）定义表类型：TYPE SUM_SALES_COUNTRY_T_TAB
CREATE TYPE sum_sales_country_t_tab AS TABLE OF sales_country_t;
（3）定义对象类型：TYPE sales_gender_t
CREATE TYPE sales_gender_t AS OBJECT (
   YEAR              VARCHAR2 (4),
   country_id        CHAR (2),
   cust_gender       CHAR (1),
   sum_amount_sold   NUMBER
);
（4）定义表类型：TYPE SUM_SALES_GENDER_T_TAB
CREATE TYPE sum_sales_gender_t_tab AS TABLE OF sales_gender_t;
（5）定义对象类型：TYPE sales_roll_t
CREATE TYPE sales_roll_t AS OBJECT (
   channel_desc      VARCHAR2 (20),
   country_id        CHAR (2),
   sum_amount_sold   NUMBER
);
（6）定义表类型：TYPE SUM_SALES_ROLL_T_TAB
CREATE TYPE sum_sales_roll_t_tab AS TABLE OF sales_roll_t;
（7）检查一下建立的类型
SELECT object_name, object_type, status
  FROM user_objects
 WHERE object_type = 'TYPE';
 
4. 定义包：Create package and define REF CURSOR
CREATE OR REPLACE PACKAGE cursor_pkg
IS
   TYPE sales_country_t_rec IS RECORD (
      YEAR              VARCHAR (4),
      country           CHAR (2),
      sum_amount_sold   NUMBER
   );

   TYPE sales_gender_t_rec IS RECORD (
      YEAR              VARCHAR2 (4),
      country_id        CHAR (2),
      cust_gender       CHAR (1),
      sum_amount_sold   NUMBER
   );

   TYPE sales_roll_t_rec IS RECORD (
      channel_desc      VARCHAR2 (20),
      country_id        CHAR (2),
      sum_amount_sold   NUMBER
   );

   TYPE sales_country_t_rectab IS TABLE OF sales_country_t_rec;

   TYPE sales_roll_t_rectab IS TABLE OF sales_roll_t_rec;

   TYPE strong_refcur_t IS REF CURSOR
      RETURN sales_country_t_rec;

   TYPE row_refcur_t IS REF CURSOR
      RETURN sum_sales_country_mv%ROWTYPE;

   TYPE roll_refcur_t IS REF CURSOR
      RETURN sales_roll_t_rec;

   TYPE refcur_t IS REF CURSOR;
END corsor_pkg;

 

5. 定义表函数
（1）定义表函数：FUNCTION Table_Ref_Cur_Week
CREATE OR REPLACE FUNCTION table_ref_cur_week (cur CURSOR.refcur_t)
   RETURN sum_sales_country_t_tab
IS
   YEAR              VARCHAR (4);
   country           CHAR (2);
   sum_amount_sold   NUMBER;
   objset            sum_sales_country_t_tab := sum_sales_country_t_tab ();
   i                 NUMBER                  := 0;
BEGIN
   LOOP
-- Fetch from cursor variable
      FETCH cur
       INTO YEAR, country, sum_amount_sold;

      EXIT WHEN cur%NOTFOUND;
                       -- exit when last row is fetched
-- append to collection
      i := i + 1;
      objset.EXTEND;
      objset (i) := sales_country_t (YEAR, country, sum_amount_sold);
   END LOOP;

   CLOSE cur;

   RETURN objset;
END;
/
（2）定义表函数：FUNCTION Table_Ref_Cur_Strong
CREATE OR REPLACE FUNCTION table_ref_cur_strong (cur cursor_pkg.strong_refcur_t)
   RETURN sum_sales_country_t_tab PIPELINED
IS
   YEAR              VARCHAR (4);
   country           CHAR (2);
   sum_amount_sold   NUMBER;
   i                 NUMBER      := 0;
BEGIN
   LOOP
      FETCH cur
       INTO YEAR, country, sum_amount_sold;

      EXIT WHEN cur%NOTFOUND;                   -- exit when last row fetched
      PIPE ROW (sales_country_t (YEAR, country, sum_amount_sold));
   END LOOP;

   CLOSE cur;

   RETURN;
END;
/
（3）定义表函数：FUNCTION Table_Ref_Cur_row
CREATE OR REPLACE FUNCTION table_ref_cur_row (cur cursor_pkg.row_refcur_t)
   RETURN sum_sales_country_t_tab PIPELINED
IS
   in_rec    cur%ROWTYPE;
   out_rec   sales_country_t := sales_country_t (NULL, NULL, NULL);
BEGIN
   LOOP
      FETCH cur
       INTO in_rec;

      EXIT WHEN cur%NOTFOUND;                -- exit when last row is fetched
      out_rec.YEAR := in_rec.YEAR;
      out_rec.country := in_rec.country;
      out_rec.sum_amount_sold := in_rec.sum_amount_sold;
      PIPE ROW (out_rec);
   END LOOP;

   CLOSE cur;

   RETURN;
END;
/
（4）定义表函数：FUNCTION Gender_Table_Ref_Cur_Week
CREATE OR REPLACE FUNCTION gender_table_ref_cur_week (cur cursor_pkg.refcur_t)
   RETURN sum_sales_gender_t_tab
IS
   YEAR              VARCHAR2 (4);
   country_id        CHAR (2);
   cust_gender       CHAR (1);
   sum_amount_sold   NUMBER;
   objset            sum_sales_gender_t_tab := sum_sales_gender_t_tab ();
   i                 NUMBER                 := 0;
BEGIN
   LOOP
      FETCH cur
       INTO YEAR, country_id, cust_gender, sum_amount_sold;

      EXIT WHEN cur%NOTFOUND;                -- exit when last row is fetched
      i := i + 1;
      objset.EXTEND;
      objset (i) :=
          sum_sales_gender_t (YEAR, country_id, cust_gender, sum_amount_sold);
   END LOOP;

   CLOSE cur;

   RETURN objset;
END;
/

6. 调用表函数
下列 SQL 查询语句调用已被定义的表函数。
SELECT *
  FROM TABLE (table_ref_cur_week (CURSOR (SELECT *
                                            FROM sum_sales_country_mv)));

SELECT *
  FROM TABLE (table_ref_cur_strong (CURSOR (SELECT *
                                              FROM sum_sales_country_mv)));

SELECT *
  FROM TABLE (table_ref_cur_row (CURSOR (SELECT *
                                           FROM sum_sales_country_mv)));

SELECT *
  FROM TABLE (table_ref_cur_week (CURSOR (SELECT *
                                            FROM sum_sales_country_mv
                                           WHERE country = 'AU')));