After update trigger result different with 5.0 and 5.1

[Yung-Chi Yang]

Hi,

We are planning to upgrade our old MySQL system from 5.0.96 to 5.1.73.
but after upgraded we found some problem on the trigger function.

We have a trigger that will insert new record into BB table after AA updated.
But we found if the update action on AA table but no row been changed.
Then BB table be inserted new record in MySQL 5.1.73.
But in MySQL 5.0.96 no row be inserted.

There is a simple test case below and could found the difference easily.

mysql> CREATE TABLE AA (a INT, b INT);
mysql> CREATE TABLE BB (a INT, b INT);
mysql> INSERT INTO AA VALUES(1,1);
mysql> INSERT INTO AA VALUES(2,2);
mysql> INSERT INTO AA VALUES(3,3);
mysql> CREATE TRIGGER test_trigger AFTER UPDATE ON AA FOR EACH ROW
-> INSERT INTO BB VALUES(NEW.a, NEW.b);

mysql> UPDATE AA SET b=3 WHERE a=3;

****** the result on MySQL 5.1.73 *****

Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0

mysql> SELECT * FROM BB;
+------+------+
| a | b |
+------+------+
| 3 | 3 |
+------+------+
1 row in set (0.00 sec)

***** the result on MySQL 5.0.96 *****

Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0

mysql> SELECT * FROM BB;
Empty set (0.00 sec)

We want to know how to make MySQL 5.1.73 have the some result with 5.0.96.
Is there anybody to could help us to solve this problem?

Thanks.

Best Regard,
Rio