na nemazé, hogy védjem, de:
mysql> create table blabla (
-> bla int not null
-> );
Query OK, 0 rows affected (0.09 sec)
mysql>
mysql> insert into blabla values (1);
Query OK, 1 row affected (0.09 sec)
mysql>
mysql> update blabla set bla = null;
Query OK, 1 row affected, 1 warning (0.10 sec)
Rows matched: 1 Changed: 1 Warnings: 1
mysql> show warnings;
+---------+------+-----------------------------+
| Level | Code | Message |
+---------+------+-----------------------------+
| Warning | 1048 | Column 'bla' cannot be null |
+---------+------+-----------------------------+
1 row in set (0.00 sec)
mysql> select * from blabla;
+-----+
| bla |
+-----+
| 0 |
+-----+
1 row in set (0.00 sec)
mysql Ver 14.14 Distrib 5.5.24, for Linux (i686) using readline 5.1