Error using filter function mapping

Hi,

I'm trying to user the function filter but it's not working as I expected.

I have a list of elements with the next structure:

ITEMS

           ERROR_CODE

           DESCRIPTION

And I have to filter the elements that has error code 000.

So I'm trying to perform a mapping using the filter function in the next way:

filter(ITEMS,"ERROR_CODE=000")

But it's always returning an empty list.

Any ideas??

Thanks.

Jorge