Subject Re: Adding a field with NOT NULL constraint
Author Dmitry Yemanov
10.02.2018 22:33, Aldo Caruso wrote:
> A strange behavior is seen in the combination not null and no default
> value. It is returned as a 0 for selects but treated as a NULL when
> comparing.

In fact, the engine returns NULL. But query prepare describes the output
descriptor as NOT NULL. Some connectivity layers (including ISQL, IIRC)
get fooled, as NULL is not expected from a NOT NULL descriptor, and zero
/ empty string is returned. I recall that IBExpert is able to return
NULL in this case.