A brief analysis of the application of table functions in Oracle

The table function can accept query statements or cursors as input parameters, and can output multiple rows of data. This function can be executed in parallel and continuously output a stream of data, which is called pipelined output. Applying table functions handles data transformation in stages and eliminates the need for storage and buffering tables of intermediate results.

1. Use a cursor to transfer data

Use the cursor REF CURSOR to pass the data set (multiple row records) to the PL/SQL function:

SELECT *
 FROM TABLE (myfunction (CURSOR (SELECT *
         FROM mytab)));

2. Use two materialized views (or tables) as template data

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. Define object types and table types based on object types

Define object types and prepare them for further references.

(1) Define the object type: TYPE sales_country_t

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;

(2) Define the table type: TYPE SUM_SALES_COUNTRY_T_TAB

CREATE TYPE sum_sales_country_t_tab AS TABLE OF sales_country_t;

(3) Define the object type: 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) Define the table type: TYPE SUM_SALES_GENDER_T_TAB

CREATE TYPE sum_sales_gender_t_tab AS TABLE OF sales_gender_t;

(5) Definition of object type: TYPE sales_roll_t

CREATE TYPE sales_roll_t AS OBJECT (
 channel_desc  VARCHAR2 (20),
 country_id  CHAR (2),
 sum_amount_sold NUMBER
);

(6) Definition Table type: TYPE SUM_SALES_ROLL_T_TAB

CREATE TYPE sum_sales_roll_t_tab AS TABLE OF sales_roll_t;

(7) Check the created type

SELECT object_name, object_type, status
 FROM user_objects
 WHERE object_type = 'TYPE';

4. Create package and define REF CURSOR

CREATE OR REPLACE PACKAGE cursor_pkg
I 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. Define table function

(1) Define table function: 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) Define table function: 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 ) Define table function: 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) Define table function: 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. Call table functions

The following SQL query statements call defined table functions.

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')));

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