Обсуждение: NOT NULL and postgres 6.5.2

Hello all,

I have an table like this:

CREATE TABLE anzeigen (
...
       name                    varchar(30) NOT NULL,
...
);

The following statement _will_ be inserted:

INSERT INTO anzeigen ( ... name ...) 
VALUES ( ..., '', ...);

What is my problem?

Thanks in advance

Stephan Bauer

Stephan Bauer wrote: >Hello all, > >I have an table like this: > >CREATE TABLE anzeigen ( >... > >        name
         varchar(30) NOT NULL, >... >); > >The following statement _will_ be inserted: > >INSERT INTO anzeigen ( ...
name...)  >VALUES ( ..., '', ...); > >What is my problem?
 
An empty string is not the same as null.  It is a real value whereas null
is an unknown/undefined/irrelevant value.

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Stephan Bauer <stephan_bauer@gmx.de> writes:
> CREATE TABLE anzeigen (
> ...
>         name                    varchar(30) NOT NULL,
> ...
> );

> The following statement _will_ be inserted:

> INSERT INTO anzeigen ( ... name ...) 
> VALUES ( ..., '', ...);

> What is my problem?

An empty string '' is quite different from a NULL.

If you want to forbid empty strings you could add a constraint
expression, eg, CHECK (name <> '').
        regards, tom lane