Rajesh Kumar Mallah wrote:
>
> MySQL does not thinks 0 to be a valid integer data .
> Although 0 is not present in master table
> it allows inserting in a referencing table
> as though 0 == NULL . This is really funny (dangerous)
What does it do if you have a NOT NULL constraint on the FK column and
insert 0?
Jan
>
>
> mysql> alter table slave add foreign key (id2) references master(id);
> Query OK, 6 rows affected (0.00 sec)
> Records: 6 Duplicates: 0 Warnings: 0
>
>
> mysql> select * from master;
> Empty set (0.00 sec)
>
> mysql>
>
>
> mysql> select * from slave;
> +------+
> | id2 |
> +------+
> | 0 |
> | 0 |
> | 0 |
> | 0 |
> | 0 |
> | 0 |
> +------+
> 6 rows in set (0.00 sec)
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