SQL -not returning records with null values

[Gerald Magnuson <gmagqcy.midrange@xxxxxxxxx>]

we have been coding our loops as follows:

dow  sqlcod <> 100

....fetch records
if sqlcod<> 100
... write subfile, or write report line



evidently, the records with nulls return the 100?

we knew we should have had more records on the display,
but when we changed the if to "sqlcod = 0"
we received the records with null fields.

is this the proper fix, or is something else going on?