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Oracle 中 table 函数的应用浅析

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[数据库(综合) 所属分类 数据库(综合) | 发布者 店小二03 | 时间 | 作者 红领巾 ] 0人收藏点击收藏

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脚本之家网站的支持!

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