Re: why the need for is null?

Baldur Norddahl wrote:

> Quoting Martijn van Oosterhout <kleptog(at)svana(dot)org>:
>
...

>>You could create a new operator, but that means you'll have difficulty
>>moving it to any database that doesn't have that operator (which is most of
>>them).
>>
>>
>
>Any commercial database vendor would be happy to make such a feature just for
>that reason: to lock me in to their database :-). I do not try to stay database
>neutral, and use lots of other features that will only work in postgresql.
>
>
There already is an operator, and it is the ANSI SQL operator "IS". Just
because "IS" does not use puctuation characters does not mean it is not
an operator.

>>If you want it to match perhaps you should forget NULL and use '' (zero
>>length string) instead.
>>
>>
An empty string is an empty string, and a NULL is the lack of there being a string, they are not the same. If you want to emulate what you have proposed then use the function "coalesce".

Example:

select coalesce(string_column,'') from some_table ;

This will return an empty string for all records that have no data in
string_column.

I have designed a number of realtime data collection programs, and when inserting only the available data into the proper columns of the table, I often end up will "NULL" columns because there was no data for that column. It is very usefull to know if you had data available or if the data was 0 or an empty string.

If you still don't understand, then use MySQL it is messed up and allows weird things like most of what you want to do.

Happy New Year