Oracle中table函数的应用有哪些？

来源：www.45fan.com 2017-01-04 14:05:55

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 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）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
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. 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')));

以上所述是小编给大家介绍的Oracle 中 table 函数的应用浅析，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对路饭网站的支持！

路由器

电脑

手机

网络

Oracle中table函数的应用有哪些？

推荐阅读