Re: NULL value comparison

2012/8/22 Michael Sacket <msacket(at)gammastream(dot)com>:
> Good Day,
>
> I'm trying to figure out why a postgresql query doesn't return what I'd expect with a query like this where there are NULL values:
>
> select * from users where is_enabled<>'Y';
>
> I'm expecting it to return all records where is_enabled is 'N' or NULL. Perhaps my expectations are misguided. Any thoughts would be appreciated.

no - NULL is not comparable with any value

your query should be

WHERE is_enabled <> 'Y' or is_enabled IS NULL

or

WHERE is_enabled IS DISTINCT FROM 'Y'

Regards

Pavel Stehule

>
> Thanks!
> Michael
>
>
> Example:
>
> CREATE TABLE users (
> "name" char(50) NOT NULL,
> "is_enabled" char
> )
>
> insert into users (name, is_enabled) values ('Michael', 'Y');
> insert into users (name, is_enabled) values ('Jeremy', 'N');
> insert into users (name, is_enabled) values ('Sherry', NULL);
>
>
> select * from users where is_enabled<>'Y';
> +----------------------------------------------------+------------+
> | name | is_enabled |
> +----------------------------------------------------+------------+
> | Jeremy | N |
> +----------------------------------------------------+------------+
> 1 rows in set (0.03 sec)
>
>
>
>
>
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