What is this type of searching called? Need assistance please.

Question

version: 11.2.0.2
sparc64
I have a requirement to create a view from an xmltype column. One of the columns would be:
/Invoice/ReferenceNumbers/ReferenceNumberType=PURCHASE_ORDER_NUMBER/ReferenceNumber...and the respective fragment would look like:
<ReferenceNumbers>
    <ReferenceNumber>
       <ReferenceNumber>?</ReferenceNumber>
       <Description>?</Description>
       <ReferenceNumberType>?</ReferenceNumberType>
     </ReferenceNumber>
</ReferenceNumbers>Being that the node is generically named "ReferenceNumber," what is it called when I need to search the "ReferenceNumberType" by a particular string - in this case, the PURCHASE_ORDER_NUMBER?
select m.*
    from INVOICE i,
         xmlTable
            '$i/Invoice'
            passing i.doc as "i"
            columns
            INVOICE_NUMBER PATH '/Invoice/InvoiceHeader/invoiceNumber/text()',
            PO_NUMBER path '/Invoice/ReferenceNumbers/ReferenceNumberType=PURCHASE_ORDER_NUMBER/ReferenceNumber/text()'
         ) m
/* I know this is incorrect, but trying to detail what I'm getting after */Any help would be appreciated...I'll research how to do that in sql xquery, I just don't know what it's called.
Thank you in advance.

Answer 1

You're close. You just need a correct XPath expression.
SELECT x.*
FROM invoice t
   , XMLTable(
       '$i/Invoice'
       passing i.doc as "i"
       columns
         invoice_number number path 'InvoiceHeader/invoiceNumber'
       , po_number      number path 'ReferenceNumbers/ReferenceNumber[ReferenceNumberType="PURCHASE_ORDER_NUMBER"]/ReferenceNumber'
     ) x
/  The part between square brackets is an XPath predicate, it restricts the selected ReferenceNumber elements to those having a child ReferenceNumberType = "PURCHASE_ORDER_NUMBER", then the rest of the expression selects the child named ReferenceNumber (assuming it's not an error).