A quick observation- We have a 3rd party system inserting data into JDE's Oracle database. This system is writing Null in EDCT and EDSP fields of a custom table. To my surprise Data selection of <=Blank selects Null records in EDSP column. But same data selection on EDCT fails (due to reasons discussed here). May be EDSP being a "character" data type plays a role in this...Gene,
the reason your comparison works is that generic JDE tables do not have null values in their columns. One of the layers always ensures that blank or zero (depending on datatype) is written to the table.
Of course its still possible to have null values when updating by using non jde toolset (SQL, etc) or when dealing with foreign tables . . .