SQL & PL/SQL

Hi...
I am using oracle 10g and was trying to link the base tables of p2p cycle and need help on my query:

select prla.unit_meas_lookup_code "UNIT",
prha.type_lookup_code"PR TYPE",
prha.segment1"PR NUMBER",
prha.creation_date,null"SUPPLIER",
null"INVENTORY CATEGORY",
null"MFG NO",
null"BUYER",
null"CUSTOMER",
prla.item_id"ITEM CODE",
apia.invoice_num"INVOICE NO" ,
prla.item_description "DESCRIPTION",
null"RFQ No",
null "RFQ Date",
null"RFQ Supplier",
null "QTN No",
null "QTN Date",
pha.segment1"PO NO",
pha.vendor_id"SUPPLIER",
pha.CREATION_DATE "PO DATE",
null"ACK.DATE",
null"NO OF DAYS FROM PR TO PO",
null "ASBN NO",
rsh.receipt_num "RECEIPT NO",
null"RECEIPT DATE",
rsh.invoice_num"INVOICE NO",
null"INSPECTION DATE",
null "INSPECTION RESULT",
null"STOCKING DATE",
null "NO OF DAYS FROM PO TO RECEIPT",
null"PV NO",apca.amount "RELEASE AMOUNT",
apca.released_date "PAYMENT RELEASE DATE",
apca.payment_method_code " RELEASE MODE",
null " DAYS TAKEN "

from PO_REQUISITION_HEADERS_ALL prha,
PO_REQUISITION_LINES_ALL prla,
PO_HEADERS_ALL pha,
RCV_SHIPMENT_HEADERS rsh,
AP_INVOICE_DISTRIBUTIONS_ALL apida,
AP_INVOICES_ALL apia,
PO_DISTRIBUTIONS_ALL pda,
PO_REQ_DISTRIBUTIONS_ALL prda,
RCV_SHIPMENT_LINES rsl,
AP_CHECKS_ALL apca,
AP_INVOICE_PAYMENTS_ALL apipa

where prha.REQUISITION_HEADER_ID = prla.REQUISITION_HEADER_ID
AND prla.REQUISITION_LINE_ID = prda.REQUISITION_LINE_ID
AND prda.DISTRIBUTION_NUM = pda.DISTRIBUTION_NUM
AND pda.PO_HEADER_ID = pha.PO_HEADER_ID
AND pda.PO_DISTRIBUTION_ID = rsl.PO_DISTRIBUTION_ID
AND rsl.SHIPMENT_HEADER_ID = rsh.SHIPMENT_HEADER_ID
AND pda.PO_DISTRIBUTION_ID = apida.PO_DISTRIBUTION_ID
AND apida.INVOICE_ID = apipa.INVOICE_ID
AND apipa.CHECK_ID = apca.CHECK_ID


Cant figure out what I have missed.Please help!!!