PRAGMA AUTONOMOUS_TRANSACTION(自治事务)

这段时间遇到一个问题，程序里明明插入了一条记录，但在后边的一段Procedure中却查不到刚刚插入的记录,最后发现这个Procedure的定义中加入了PRAGMA AUTONOMOUS_TRANSACTION。

PRAGMA AUTONOMOUS_TRANSACTION中文翻译过来叫“自治事务”（翻译的还算好理解），对于定义成自治事务的Procedure，实际上相当于一段独立运行的程序段，这段程序不依赖于主程序，也不干涉主程序

自治事务的特点

第一,这段程序不依赖于原有Main程序，比如Main程序中有未提交的数据，那么在自治事务中是查找不到的。

第二,在自治事务中，commit或者rollback只会提交或回滚当前自治事务中的DML，不会影响到Main程序中的DML。

Autonomous Transaction Demo 1

Without Pragma Autonomous Transaction

CREATE TABLE t (
test_value VARCHAR2(25));

CREATE OR REPLACE PROCEDURE child_block IS

BEGIN
  INSERT INTO t
  (test_value)
  VALUES
  ('Child block insert');
  COMMIT;
END child_block;
/

CREATE OR REPLACE PROCEDURE parent_block IS

BEGIN
  INSERT INTO t
  (test_value)
  VALUES
  ('Parent block insert');

   child_block;

   ROLLBACK;
END parent_block;
/

-- run the parent procedure
exec parent_block

-- check the results
SELECT * FROM t;

Output:
Parent block insert
Child block insert

With Pragma Autonomous Transaction

CREATE OR REPLACE PROCEDURE child_block IS

PRAGMA AUTONOMOUS_TRANSACTION;

BEGIN
  INSERT INTO t
  (test_value)
  VALUES
  ('Child block insert');

  COMMIT;
END child_block;
/

CREATE OR REPLACE PROCEDURE parent_block IS

BEGIN
  INSERT INTO t
  (test_value)
  VALUES
  ('Parent block insert');

   child_block;

   ROLLBACK;
END parent_block;
/
-- empty the test table
TRUNCATE TABLE t;

-- run the parent procedure
exec parent_block;

-- check the results
SELECT * FROM t;

Output:
Child block insert

Autonomous Transaction Demo 2

Without Pragma Autonomous Transaction

DROP TABLE t;

CREATE TABLE t (testcol NUMBER);

CREATE OR REPLACE FUNCTION howmanyrows RETURN INTEGER IS
 i INTEGER;
BEGIN
  SELECT COUNT(*)
  INTO i
  FROM t;

  RETURN i;
END howmanyrows;
/

CREATE OR REPLACE PROCEDURE testproc IS
 a INTEGER;
 b INTEGER;
 c INTEGER;
BEGIN
  SELECT COUNT(*)
  INTO a
  FROM t;

  INSERT INTO t VALUES (1);
  COMMIT;

  INSERT INTO t VALUES (2);
  INSERT INTO t VALUES (3);

  b := howmanyrows;

  INSERT INTO t VALUES (4);
  INSERT INTO t VALUES (5);
  INSERT INTO t VALUES (6);
  COMMIT;

  SELECT COUNT(*)
  INTO c
  FROM t;

  dbms_output.put_line(a);
  dbms_output.put_line(b);
  dbms_output.put_line(c);
END testproc;
/

set serveroutput on

exec testproc

Output:
0
3
6
Total execution time 2.782 sec.

With Pragma Autonomous Transaction

CREATE OR REPLACE FUNCTION howmanyrows RETURN INTEGER IS
 i INTEGER;

 PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
  SELECT COUNT(*)
  INTO i
  FROM t;

  RETURN i;
END howmanyrows;
/

-- empty the test table
TRUNCATE TABLE t;

exec testproc;

Output:
0
1
6

转载请注明出处: http://blog.csdn.net/pan_tian/article/details/7675800