For what purpose the ?? marks are used in the following query

Question

Hi,
can anybody guide me the purpose of using the ?? in the given scrip,
i.e
SELECT GJL.period_name Period_Name,
GJH.je_source Je_Source,
GJH.posted_date Posted_Date, GCC.segment1||'-'||GCC.segment2||'-'||GCC.segment3||'-'||GCC.segment4||'-'||GCC.segment5||'-'||GCC.segment6||'-'||GCC.segment7||'-'||GCC.segment8 "Account",
GJL.description Description,
PH.segment1 PO#,
PV.segment1 Vendor#,
PV.vendor_name Vendor_Name,
PL.line_num PO_Line#,
PPA.segment1 Project,
GJL.reference_5 Invoice#,
GJL.reference_3 Invoice_Dist_Line#,
AIA.invoice_amount invoice_amount,
NVL(GJL.accounted_dr,0) - NVL(GJL.accounted_cr,0) Amount,
MSIB.segment1 part_no#,
PVSA.vendor_site_code site_code,
PLLB.qr Qty_received,
PLLB.qb Qty_billed,
IDA.quantity_invoiced qty_invoiced,
IDA.quantity_variance qty_discrepency,
IDA.unit_price "INV Unit Price Var",
PL.unit_price "PO Line Unit Price"
FROM
APPS.GL_JE_LINES GJL,
APPS.GL_JE_HEADERS GJH,
APPS.GL_CODE_COMBINATIONS GCC,
APPS.AP_INVOICE_DISTRIBUTIONS_ALL IDA,
APPS.PA_PROJECTS_ALL PPA,
APPS.AP_INVOICES_ALL AIA,
APPS.PO_DISTRIBUTIONS_ALL PDA,
APPS.PO_HEADERS_ALL PH,
APPS.PO_LINES_ALL PL,
APPS.PO_VENDORS PV,
APPS.PO_VENDOR_SITES_ALL PVSA,
(SELECT
PLLA.po_header_id,
PLLA.po_line_id,
SUM(PLLA.quantity_received) qr,
SUM(PLLA.quantity_billed) qb
FROM APPS.PO_LINE_LOCATIONS_ALL PLLA
GROUP BY PLLA.po_header_id,
PLLA.po_line_id) PLLB,
(select
inventory_item_id,
segment1
from APPS.MTL_SYSTEM_ITEMS_B
where organization_id = 4) MSIB
WHERE
GJL.period_name IN (gjl.period_name)
AND GJL.code_combination_id = GCC.code_combination_id
AND GCC.segment2 IN (?Segment2?)
AND GCC.segment1 IN (?Segment1?)
AND GCC.SEGMENT3 = '0'
AND (GCC.SEGMENT4 = '0' OR (GCC.segment2 IN (?Segment2?)/*='513000000'*/ AND GCC.SEGMENT4 = 'V'))
AND GCC.SEGMENT5 IN( ?Segment5? )
AND GJH.je_header_id = GJL.je_header_id
AND GJH.je_source = 'Payables'
AND GJL.reference_2 = TO_CHAR(AIA.invoice_id(+))
AND IDA.project_id = PPA.project_id(+)
AND GJL.reference_2 = TO_CHAR(IDA.invoice_id(+))
AND GJL.reference_3 = TO_CHAR(IDA.distribution_line_number(+))
AND IDA.po_distribution_id = PDA.po_distribution_id(+)
AND PDA.po_header_id = PH.po_header_id(+)
AND PDA.po_line_id = PL.po_line_id(+)
AND PH.vendor_id = PV.vendor_id(+)
AND GJH.set_of_books_id = 4
AND MSIB.inventory_item_id(+) = PL.item_id
AND PLLB.po_line_id(+) = PDA.po_line_id
AND PLLB.po_header_id(+) = PDA.po_header_id
AND PH.vendor_site_id = PVSA.vendor_site_id(+)

Answer 1

In some language, the question mark character is used a s bind variable place holder. When the SQL is executed, a value is bound to the variable. This means that same SQL can be used again and again, but with different variable values.
I hope this is true of the code you've posted below - and that the ?var? format is not used to replace that with a hard coded literal value before executing the SQL statement.