oracle:IF语句 Loop循环 Cursor的用法(一)

1 概述

在大多数时候我们在设计pl-sql程序的时候都遵循下面的步骤：  

打开游标 ->开始循环 -> 从游标中取值->检查那一行被返回 -> 处理 -> 关闭循环 -> 关闭游标

2 格式:复制内容到剪贴板/ 程序代码

CURSOR <游标名称> IS

<游标名称>%ROWTYPE;

BEGIN

  OPEN <游标名称>

  LOOP

    FETCH <游标名称> INTO ;

    EXIT WHEN <游标名称>%NOTFOUND;

    <其它要执行的代码>

  END LOOP;

  CLOSE <游标名称>;

END <存储过程名称>;

/

3 代码

代码例子:复制内容到剪贴板

程序代码

TRUNCATE TABLE loop_test;

DECLARE

CURSOR ao_cur IS

Select SUBSTR(object_name,1,5) FIRSTFIVE

FROM all_objs

Where SUBSTR(object_name,1,5) BETWEEN 'A' AND 'M';

ao_rec ao_cur%ROWTYPE;

BEGIN

  OPEN ao_cur;

  LOOP

    FETCH ao_cur INTO ao_rec;

    EXIT WHEN ao_cur%NOTFOUND;

    Insert INTO loop_test VALUES (ao_rec.firstfive);

  END LOOP;

  COMMIT;

  CLOSE ao_cur;

END;

/

Select COUNT(*) FROM loop_test;

[code]

Demo

[code]

Fetch Demo

Create TABLE t1 (tcol NUMBER);

Create TABLE t2 (c NUMBER);

BEGIN

  FOR i IN 1..500 LOOP

    Insert INTO t1 VALUES (i);

  END LOOP;

END;

/

Select COUNT(*) FROM t1;

COMMIT;

Create or REPLACE FUNCTION p (c_in NUMBER) RETURN NUMBER IS

PRAGMA AUTONOMOUS_TRANSACTION;

BEGIN

  -- Every time this is called, write a row to table t2

  Insert INTO t2 VALUES (c_in);

  COMMIT;

  RETURN c_in;

END p;

/

DECLARE

  BEGIN

  /* Open up a cursor for loop, also selecting

  * the "p" function which will write rows to

  * t2 for every row fetched from t1. */

  FOR crec IN (Select tcol, p(tcol) FROM t1) LOOP

    -- Break out of the loop immediately

    EXIT;

  END LOOP;

END;

/

Select COUNT(*) FROM t2;

注意:%ROWTYPE也可以用游标名来定义，但必须要首先声明游标,所以上面的例子要采用显示的游标声明

Cursor FOR Loop

格式:

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程序代码

Create or REPLACE PROCEDURE <存储过程名称> IS

CURSOR <游标名称> IS

BEGIN

  FOR IN <游标名称>

  LOOP

    <其它要执行的代码>

  END LOOP;

END <存储过程名称>;

/

代码:

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程序代码

TRUNCATE TABLE loop_test;

DECLARE

CURSOR ao_cur IS

   Select SUBSTR(object_name,1,5) FIRSTFIVE

   FROM all_objs

   Where SUBSTR(object_name,1,5) BETWEEN 'N' AND 'W';

BEGIN

  FOR ao_rec IN ao_cur LOOP

    Insert INTO loop_test VALUES (ao_rec.firstfive);

  END LOOP;

  COMMIT;

END;

/

Select COUNT(*) FROM loop_test;

Curcor For Loop是一个隐式的游标声明.

格式:

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程序代码

BEGIN

  FOR IN

  LOOP

    <其它要执行的代码>

  END LOOP;

END <存储过程名称>;

/

Demo

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程序代码

TRUNCATE TABLE loop_test;

BEGIN

  FOR ao_rec IN (

    Select SUBSTR(object_name,1,5) FIRSTFIVE

    FROM all_objs

    Where SUBSTR(object_name,1,5) BETWEEN 'N' AND 'Z')

  LOOP

    Insert INTO loop_test VALUES (ao_rec.firstfive);

  END LOOP;

  COMMIT;

END;

/

Select COUNT(*) FROM loop_test;

Cursor Loop With Where CURRENT OF Clause

格式:

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程序代码

Create or REPLACE PROCEDURE <存储过程名称> IS

BEGIN

  FOR IN (<游标名称>)

  LOOP

    <其它要执行的代码>

    Update

    SET =

    Where CURRENT OF <游标名称>

  END LOOP;

END <存储过程名称>;

/

Demo:

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程序代码     

Create TABLE test (

pid  NUMBER(3),

cash  NUMBER(10,2));

Insert INTO test VALUES (100, 10000.73);

Insert INTO test VALUES (200  25000.26);

Insert INTO test VALUES (300, 30000.11);

Insert INTO test VALUES (400, 45000.99);

Insert INTO test VALUES (500, 50000.08);

COMMIT;

Create or REPLACE PROCEDURE wco IS

CURSOR x_cur IS

Select pid, cash

FROM test

Where cash < 35000

FOR Update;

BEGIN

  FOR x_rec IN x_cur LOOP

    Update test

    SET cash = FLOOR(cash)

    Where CURRENT OF x_cur;

  END LOOP;

  COMMIT;

END wco;

/

exec wco;

Select * FROM test;

嵌套的游标循环 Nested Cursor Loops

测试样表

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程序代码     

Create TABLE airplanes (

program_id  VARCHAR2(3),

line_number NUMBER(10),

customer_id VARCHAR2(4),

order_date  DATE,

delivered_date DATE)

PCTFREE 0;

Create INDEX programid_idx

ON airplanes (program_id)

PCTFREE 0;

Create TABLE parts (

program_id VARCHAR2(3),

line_type VARCHAR2(4),

part_type VARCHAR2(10),

quantity NUMBER(3));

Create TABLE ap_parts AS

Select a.customer_id, p.part_type, p.quantity

FROM airplanes a, parts p

Where a.program_id = p.program_id

AND 1=2;

PL-SQL Example

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程序代码     

DECLARE

progid  airplanes.program_id%TYPE;

lineno  airplanes.line_number%TYPE;

custid  airplanes.customer_id%TYPE := 'AAL';

orddate airplanes.order_date%TYPE;

deldate airplanes.delivered_date%TYPE;

BEGIN

  FOR i IN 1 .. 5 LOOP

    Select DECODE(i, 1, '737', 2, '747', 3, '757', 4, '767', 5, '777')

    INTO progid

    FROM dual;

    FOR lineno IN 1..250 LOOP

      Select DECODE(custid, 'AAL','DAL','DAL','SAL','SAL','ILC',

     'ILC','SWA', 'SWA','NWO','NWO','AAL')

      INTO custid

      FROM dual;

    IF progid = '737' THEN

      ordDate := SYSDATE + lineno;

      DelDate := ordDate + lineno + 100;

    ELSIF progid = '747' THEN

      ordDate := SYSDATE + lineno+17;

      DelDate := ordDate + lineno + 302;

    ELSIF progid = '757' THEN

      ordDate := SYSDATE + lineno+22;

      DelDate := ordDate + lineno + 202;

    ELSIF progid = '767' THEN

      ordDate := SYSDATE + lineno+43;

      DelDate := ordDate + lineno + 189;

    ELSIF progid = '777' THEN

      ordDate := SYSDATE + lineno-69;

      DelDate := ordDate + lineno + 299;

    END IF;

      Insert INTO airplanes

      (program_id, line_number, customer_id, order_date,

       delivered_date)

      VALUES

      (progid, lineno, custid, orddate, deldate);

    END LOOP;

  END LOOP;

  COMMIT;

END load_airplanes;

/

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程序代码

Load Airplane Parts    BEGIN

  Insert INTO parts VALUES ('737', 'Even', 'Wing', 2);

  Insert INTO parts VALUES ('747', 'Even', 'Wing', 2);

  Insert INTO parts VALUES ('757', 'Even', 'Wing', 2);

  Insert INTO parts VALUES ('767', 'EVen', 'Wing', 2);

  Insert INTO parts VALUES ('777', 'even', 'Wing', 2);

  Insert INTO parts VALUES ('737', 'ODD', 'Wing', 2);

  Insert INTO parts VALUES ('747', 'odd', 'Wing', 2);

  Insert INTO parts VALUES ('757', 'Odd', 'Wing', 2);

  Insert INTO parts VALUES ('767', 'Odd', 'Wing', 2);

  Insert INTO parts VALUES ('777', 'Odd', 'Wing', 2);

  Insert INTO parts VALUES ('737', 'Even', 'Galley', 1);

  Insert INTO parts VALUES ('747', 'EVen', 'Galley', 3);

  Insert INTO parts VALUES ('757', 'EVEN', 'Galley', 3);

  Insert INTO parts VALUES ('767', 'EVeN', 'Galley', 2);

  Insert INTO parts VALUES ('777', 'even', 'Galley', 3);

  Insert INTO parts VALUES ('737', 'ODD', 'Galley', 2);

  Insert INTO parts VALUES ('747', 'odd', 'Galley', 4);

  Insert INTO parts VALUES ('757', 'Odd', 'Galley', 3);

  Insert INTO parts VALUES ('767', 'ODd', 'Galley', 4);

  Insert INTO parts VALUES ('777', 'odD', 'Galley', 4);

  Insert INTO parts VALUES ('737', 'Even', 'Tire', 10);

  Insert INTO parts VALUES ('747', 'Even', 'Tire', 18);

  Insert INTO parts VALUES ('757', 'Even', 'Tire', 12);

  Insert INTO parts VALUES ('767', 'Even', 'Tire', 14);

  Insert INTO parts VALUES ('777', 'EveN', 'Tire', 16);

  Insert INTO parts VALUES ('737', 'ODD', 'Tire', 14);

  Insert INTO parts VALUES ('747', 'Odd', 'Tire', 20);

  Insert INTO parts VALUES ('757', 'Odd', 'Tire', 14);

  Insert INTO parts VALUES ('767', 'Odd', 'Tire', 16);

  Insert INTO parts VALUES ('777', 'Odd', 'Tire', 18);

  Insert INTO parts VALUES ('737', 'Even', 'Seats', 105);

  Insert INTO parts VALUES ('747', 'Even', 'Seats', 255);

  Insert INTO parts VALUES ('757', 'Even', 'Seats', 140);

  Insert INTO parts VALUES ('767', 'Even', 'Seats', 200);

  Insert INTO parts VALUES ('777', 'EveN', 'Seats', 210);

  Insert INTO parts VALUES ('737', 'ODD', 'Seats', 137);

  Insert INTO parts VALUES ('747', 'Odd', 'Seats', 20);

  Insert INTO parts VALUES ('757', 'Odd', 'Seats', 166);

  Insert INTO parts VALUES ('767', 'Odd', 'Seats', 345);

  Insert INTO parts VALUES ('777', 'Odd', 'Seats', 267);

  COMMIT;

END;

/

[code]

嵌套固定的游标

Nested Loops With Static Cursors

DeMo:

[code]    

Create or REPLACE PROCEDURE nested_loop IS

CURSOR a_cur IS

Select program_id, line_number, customer_id

FROM airplanes;

a_rec a_cur%ROWTYPE;

CURSOR p_cur IS

Select part_type, quantity

FROM parts

Where program_id = a_rec.program_id

AND UPPER(line_type)=DECODE(MOD(a_rec.line_number,2),0,'EVEN','ODD');

p_rec p_cur%ROWTYPE;

BEGIN

  OPEN a_cur;

  LOOP

    FETCH a_cur INTO a_rec;

    EXIT WHEN a_cur%NOTFOUND;

    OPEN p_cur;

    LOOP

      FETCH p_cur INTO p_rec;

      EXIT WHEN p_cur%NOTFOUND;

      Insert INTO ap_parts

      (customer_id, part_type, quantity)

      VALUES

      (a_rec.customer_id, p_rec.part_type, p_rec.quantity);

    END LOOP;

    CLOSE p_cur;

  END LOOP;

  COMMIT;

  CLOSE a_cur;

END nested_loop;

/

嵌套使用BLUK COLLECT获取数据集的循环

Nested Loops with Bulk Collect

这个demo是为了显示通过BULK COLLECTION来复制嵌套循环中的游标里的数据

Demo

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程序代码

Create or REPLACE PROCEDURE bulk_nested IS

CURSOR a_cur IS

Select program_id, line_number, customer_id

FROM airplanes;

TYPE ap_array IS TABLE OF airplanes.program_id%TYPE

INDEX BY BINARY_INTEGER;

ap_rec ap_array;

TYPE al_array IS TABLE OF airplanes.line_number%TYPE

INDEX BY BINARY_INTEGER;

al_rec al_array;

TYPE ac_array IS TABLE OF airplanes.customer_id%TYPE

INDEX BY BINARY_INTEGER;

ac_rec ac_array;

TYPE pp_array IS TABLE OF parts.part_type%TYPE

INDEX BY BINARY_INTEGER;

pp_rec pp_array;

TYPE pq_array IS TABLE OF parts.quantity%TYPE

INDEX BY BINARY_INTEGER;

pq_rec pq_array;

BEGIN

  OPEN a_cur;

  LOOP

    FETCH a_cur BULK COLLECT INTO ap_rec, al_rec, ac_rec LIMIT 500;

    FOR i IN 1 .. ap_rec.COUNT LOOP

      DECLARE

        CURSOR p_cur IS

        Select part_type, quantity

        FROM parts

        Where program_id = ap_rec(i)

        AND UPPER(line_type)=DECODE(MOD(al_rec(i),2),0,'EVEN','ODD');

      BEGIN

        OPEN p_cur;

        LOOP

          FETCH p_cur BULK COLLECT INTO pp_rec, pq_rec;

          FORALL j IN pp_rec.FIRST .. pp_rec.LAST

          Insert INTO ap_parts

          (customer_id, part_type, quantity)

          VALUES

          (ap_rec(i), pp_rec(j), pq_rec(j));

          EXIT WHEN p_cur%NOTFOUND;

        END LOOP;

        CLOSE p_cur;

      END;

    END LOOP;

    EXIT WHEN a_cur%NOTFOUND;

  END LOOP;

  COMMIT;

  CLOSE a_cur;

END bulk_nested;

/