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  • 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‘)));

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  • 原文地址:https://www.cnblogs.com/soundcode/p/2311933.html
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