Subject RE: [IBO] chance Only is null
Author Support List

> Try in TIB_QUERY.
> Field(varchar or integer) is NOT NULL in Firebird 2.5. ok ?
> If field is Null then can change.
> If field contains value can not change.
> There property in IB_QUERY to do this.

There isn't a property to do this. You will need to provide a custom event
handler with the OnGetReadOnly or something of that sort. You might also be
able to call SysUtils.Abort in the OnValidate event so that it would quietly
abort making a change when the value isn't null.

Jason LeRoy Wharton