Re: what is null

> 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?
> 
John,
Try "my_id is null" instead of "my_id=NULL"