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:

复制内容到剪贴板 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:

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 '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:

复制内容到剪贴板 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

复制内容到剪贴板 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:

复制内容到剪贴板 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:

复制内容到剪贴板 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

复制内容到剪贴板 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

复制内容到剪贴板 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;
/

复制内容到剪贴板 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

复制内容到剪贴板 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;
/