Ruslan U. Zakirov wrote:
> Keith C. Ivey wrote:
>> On 14 Apr 2004 at 17:27, B. Fongo wrote:
>>> I expected a warning because of the Token column shouldn't be NULL!
>> It's not NULL. It's the empty string, which is the default value,
>> since you didn't give it a specific default value. See the "CREATE
>> TABLE" documentation:
>> If no DEFAULT value is specified for a column, MySQL
>> automatically assigns one, as follows. If the column can
>> take NULL as a value, the default value is NULL. If the
>> column is declared as NOT NULL, the default value depends on
>> the column type: [...]
>> * For string types other than ENUM, the default value is the
>> empty string.
> I didn't know this too I expect correct behavior: error.
Well, that depends on your definition of "correct". Some will argue that
the SQL standard, whatever that is, defines "correct". Others will say that
the MySQL documentation defines "correct". Either way, if you work with
MySQL, you need to know what it really does.
Because MySQL supports non-transactional table types, every column has a
default. So, if you leave a column out of your INSERT, it gets the default.
On the other hand, if you try to explicitly set a NOT NULL column to NULL
with a single row INSERT, you get an error.
> So if I want error on such INSERTs I must use 'IS NOT NULL default NULL'?
> Best regards. Ruslan.
No. You cannot set NULL as the default for a NOT NULL column (at least, not
in MySQL). If you want an error, specify NULL for the column rather than
leaving it out of your INSERT.