Re: what is null

On Monday 04 August 2003 22:54, John Harrold wrote:
> i'm trying to alter a table call it 'my_table' and i'm trying to set the
> field 'my_id' to prevent null values from being inserted. when i run the
> following:
>
> ALTER TABLE my_table ALTER my_id SET NOT NULL;
>
> i get:
>
> ERROR: ALTER TABLE: Attribute "my_id" contains NULL values
>
> so i want to find out which rows have null values so i run:
>
> my=# select my_id from my_table where my_id=NULL;
> my_id
> ---------
> (0 rows)
>
>
> so this would indicate to me that there are no rows in which my_id is NULL.
> so what is preventing me from altering the table? or am i just doing
> something wrong?

select my_id from my_table where my_id IS NULL;
or
change configuration parameter "transform_null_equals" to yes in
postgresql.conf, restart server and you can try with :
select my_id from my_table where my_id=NULL;

Regards !