Unable to pass value to Table type DFF in payables invoice

Summary:

I have drafted DFF in AP invoice header level called "Requisition Creator"

This DFF should be automatically populated with name of person who had created the requisition which was then turned to PO and subsequently to an AP invoice.

The SQL query used in the DFF is as following.

select LIST_NAME from PER_PERSON_NAMES_F
where PERSON_ID in (select PERSON_ID from PER_USERS where USERNAME in
(select CREATED_BY from POR_REQUISITION_HEADERS_ALL where REQUISITION_HEADER_ID in(
select REQUISITION_HEADER_ID from POR_REQUISITION_LINES_ALL where PO_HEADER_ID in (
select PO_HEADER_ID from PO_HEADERS_ALL WHERE segment1 = :PoNumber/*