PRAGMA AUTONOMOUS_TRANSACTION

原帖地址http://blog.csdn.net/pan_tian/article/details/7675800

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