link between purchase order and AP reserve invoice

How do I get every AP reserve invoice for a purchase order using the SQL version of SAP Business One?

My current query:

SELECT 
  OPOR.CardCode, 
  OPOR.CardName, 
  OPOR.U_ReferenceNo, 
  OPOR.NumAtCard, 
  OPOR.DocNum, 
  OPOR.U_ShipmentTime, 
  OPOR.U_DealType, 
  OPOR.DocDate, 
  OPOR.U_Origin, 
  OPOR.U_DealQuantity, 
  OPOR.U_ContainerNo, 
  POR1.ItemCode, 
  POR1.Dscription, 
  POR1.Price, 
  por1.U_CopperRate, 
  POR1.U_AluminiumRate, 
  POR1.U_IronRate, 
  POR1.U_CopperPer, 
  por1.U_AluminiumPer, 
  POR1.U_LeadPer, 
  POR1.U_IronPer, 
  POR1.U_PlasticPer 

FROM
  OPOR 
  INNER JOIN POR1 ON OPOR.DocEntry = POR1.DocEntry 

WHERE
  OPOR.DocStatus = 'o'

You can use sap.erpref.com to get more details about every table on a SAP Business one SQL schema.

The A/P invoice table is OPCH, and the field reserve means it is a A/P reserve invoice.

So your select should be like this:

SELECT 
  OPOR.CardCode,
  MAX(OPOR.CardName), 
  MAX(OPOR.U_ReferenceNo), 
  MAX(OPOR.NumAtCard), 
  MAX(OPOR.DocNum), 
  MAX(OPOR.U_ShipmentTime), 
  MAX(OPOR.U_DealType), 
  MAX(OPOR.DocDate), 
  MAX(OPOR.U_Origin), 
  MAX(OPOR.U_DealQuantity), 
  MAX(OPOR.U_ContainerNo), 
  MAX(POR1.ItemCode), 
  MAX(POR1.Dscription), 
  MAX(POR1.Price), 
  MAX(POR1.U_CopperRate), 
  MAX(POR1.U_AluminiumRate), 
  MAX(POR1.U_IronRate), 
  MAX(POR1.U_CopperPer), 
  MAX(POR1.U_AluminiumPer), 
  MAX(POR1.U_LeadPer), 
  MAX(POR1.U_IronPer), 
  MAX(POR1.U_PlasticPer),
  COUNT(OPCH. DocNum)

FROM
  OPOR 
  LEFT JOIN POR1 ON OPOR.DocEntry = POR1.DocEntry 
  LEFT JOIN OPCH ON OPOR.DocEntry = OPCH.DocEntry

WHERE
  OPOR.DocStatus = 'o'
  AND OPCH.reserve = 'Y'
  
 GROUP BY
    OPOR.CardCode