Help with XQueriyng an AWS XML file

Question

--Oracle Database 11g Express Edition Release 11.2.0.2.0 - Beta
I am trying to query an XML file returned from Amazon AWS. I'm learning this slowly, and i think examples would really help . I'm reading and looking through the documentation " [Using XQuery with Oracle XML DB|http://docs.oracle.com/cd/E11882_01/appdev.112/e23094/xdb_xquery.htm] ".
I made an batch of 2 ItemLookup requests to AWS, which returned one item for the first lookup, and two for the second, which i think is a good example. I used a bogus account id (it's used for tracking) and a key pair which i deleted after using it, so it is the actual reply. It is too large to be passed as a literal, so i put it on pastebin. It shows a valid request. There are two levels of validity, one is no error, the other IsValid. Had there been an error, like a missing parameter, the following would be between the </Arguments> and <RequestProcessingTime> tags:
    <Errors>
      <Error>
        <Code>AWS.MissingParameters</Code>
        <Message>Your request is missing required parameters. Required parameters include ItemId.</Message>
      </Error>
    </Errors>Meaning, first the XML document must be checked for the Errors tag; second, the IsValid element must be True; third, actual data can be perused. The Errors tag mean there may be multiple errors. The IsValid is per Items (not Item). Then individual details may be grabbed, such as ListPrice.
I'm guessing XQuery is the right way to go here, using XMLTABLE to create records to be queried. Here is what i have so far:
SELECT
FROM
     XMLTABLE
      XMLNAMESPACES(DEFAULT 'http://webservices.amazon.com/AWSECommerceService/2011-08-01'),
      '/ItemLookupResponse/OperationRequest/Errors/Error,
     for $Error in /ItemLookupResponse/OperationRequest/Errors/Error
       return
          <Error>
           $Error/Code,
           $Error/Message
          </Error>,
      for $Item in /ItemLookupResponse/Items
       return
          <Item>
           $Item/Request/IsValid
          </Item>'
      PASSING
          (code to get XML document: e.g. ItemLookup('036500101794', 'UPC', 'OfficeProducts', '5011363525517', 'EAN', 'Toys'))
      COLUMNS
          Id FOR ORDINALITY,
          Error_Code     VARCHAR2(10) PATH 'Code',
          Error_Message     VARCHAR2(10) PATH 'Message',
          IsValid          VARCHAR2(05) PATH 'IsValid'
     );Of which the response is:
        ID ERROR_CODE ERROR_MESS ISVAL
         1                       True
         2                       TrueOstensibly, there are no errors, so the first record is the IsValid element for the first Items tag, and the second for the second. Now, i need to loop inside each Items for all of its Item tags.
1) Is this a good approach. I ask because this is really my first XQuery.
2) Is the for loop for Errors good? I am assuming it will only have a record if there is an error.
3) Do i nest for loops to get each Item in each Items?
4) How do i know which Items is being used when in the (sub) Item tag?
I would appreciate any help. It just hasn't "clicked" yet, and i am having a hard time knowing what to do.

Answer 1

OK, figured it out....The XMLTABLE does the join, so the FULL JOIN is simply not required:
Making the final code:
     WITH
          XML(Document)
     AS
           SELECT
               Amazon_PAPI.Get_Response(Amazon_PAPI.ItemLookup('036500101794', 'UPC', 'OfficeProducts', '5011363525517', 'EAN', 'Toys'))
           FROM
               Dual
     SELECT
          Items.Id,
          Items.Code,
          Items.Message,
          Items.Isvalid,
          Item.Id Item_Id,
          Item.ASIN
     FROM
          XMLTABLE
           XMLNAMESPACES(DEFAULT 'http://webservices.amazon.com/AWSECommerceService/2011-08-01'),
           '/ItemLookupResponse/OperationRequest/Errors/Error
           | /ItemLookupResponse/Items'
           PASSING
               (SELECT Document FROM XML)
           COLUMNS
                Id          FOR ORDINALITY,
               Code          VARCHAR2(0050)     PATH 'Code',
               Message          VARCHAR2(4000)     PATH 'Message',
               IsValid          VARCHAR2(005)     PATH 'Request/IsValid',
               Item          XMLTYPE          PATH 'Item'
          ) Items
     LEFT JOIN
          XMLTABLE
           XMLNAMESPACES(DEFAULT 'http://webservices.amazon.com/AWSECommerceService/2011-08-01'),
           '/Item'
           PASSING
               Items.Item
           COLUMNS
               Id                    FOR ORDINALITY,
               ASIN                    VARCHAR2(0010)     PATH 'ASIN'
          ) Item
      ON
          1 = 1
     ORDER BY
          Items.Id,
          Item.Id;With the result, when successful:
        ID CODE                                     MESSAGE                                            ISVAL    ITEM_ID ASIN
         1                                                                                             True       1 B004WL0L9S
         2                                                                                             True       1 B0042ET8OO
         2                                                                                             True       2 B00004TQMQAnd when not successful:
        ID CODE                                     MESSAGE                                            ISVAL    ITEM_ID ASIN
         1 AWS.InvalidEnumeratedParameter           The value you specified for IdType is invalid.
                                                    Valid values include ['ASIN', 'SKU',
                                                    'UPC', 'EAN','ISBN'].
         2 AWS.RestrictedParameterValueCombination  Your request contained a restricted parameter
                                                    combination.  When IdType equals UPCa, SearchIndex
                                                    cannot be present.Still looking to test a no-error IsValid = False case though. :)