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DBMS_XMLQUERY vs. DBMS_XMLGEN

Oracle Database Tips by Donald BurlesonMarch 10, 2015


The following issue came up for one of our forum users while creating a webservice to return nested XML data. The data contains a special character that prevented IE 6.0 from displaying the XML output.

    <Plant num="4">
      <TypeCode>PFL</TypeCode>
      <TypeDesc>Plant</TypeDesc>
      <Code>ABAXA</Code>
      <PrefScientificName>Arracacia xanthorrhiza</PrefScientificName>
      <PrefCommonName>Arracacha</PrefCommonName>
      <CommonNames>
         <CommonNames_ROW num="3">
            <Language>French</Language>
            <CommonName>Pomme de terre céleri</CommonName>
         </CommonNames_ROW>
      </CommonNames>
    </Plant>

By default, XMLGEN generates an xml header <?xml version = '1.0'?>

This generates the IE 6.0 error because of the accent marked e in céleri.

By converting to DBMS_XMLQUERY, he could set the XML header to his company standard encoding
<?xml version = '1.0' encoding = 'ISO-8859-1'?>
, and the webservice works just fine.

The code is almost identical. The irrelevant portions are snipped out here.

    qryCtx := DBMS_XMLQuery.newContext(v_prd_query);
    --
    --  Set the encoding tag to handle Unicode
    --
    DBMS_XMLQuery.setEncodingTag(qryCtx, 'ISO-8859-1');
    DBMS_XMLQuery.setRowsetTag(qryCtx, 'root');
    DBMS_XMLQuery.setRowTag(qryCtx, v_bayer_group_tag);
    --
    --  Set up the bind variables.
    --  Note: DBMS_XMLQuery cannot handle a bind variable occurring more than once.
    --
    DBMS_XMLQuery.setbindvalue (qryCtx, 'cp_bayer_group', UPPER(i_bayer_group));
    DBMS_XMLQuery.setbindvalue (qryCtx, 'cp_filter1',      UPPER(i_filter));
    DBMS_XMLQuery.setbindvalue (qryCtx, 'cp_filter2',      UPPER(i_filter));
    DBMS_XMLQuery.setbindvalue (qryCtx, 'cp_filter3',      UPPER(i_filter));
    --
    --  Execute the query and put the results into the CLOB
    --
    o_results := DBMS_XMLQuery.getXML(qryCtx);
    --
    --  Close the context
    --
    DBMS_OUTPUT.PUT_LINE('Close Context');
    DBMS_XMLQuery.closeContext(qryCtx);

As you can see from the comment, he learned that multiple occurrences of a bind variable does not work in DBMS_XMLQUERY. You receive the following error:

oracle.xml.sql.OracleXMLSQLException: Missing IN or OUT parameter at index:: 2

Where the index refers to which occurrence of a bind variable (starting at 0) failed. In this case, it was the third bind_variable occurrence that failed.

      || 'FROM   sde_bayer_code_pref_names_v bc' || CHR(10)
      || '      ,(SELECT bc2.type_code    AS type_code' || CHR(10)
      || '              ,bc2.code_seq_id  AS code_seq_id' || CHR(10)
      || '        FROM   sde_bayer_code_pref_names_v bc2' || CHR(10)
      || '        WHERE  UPPER(bc2.code) like UPPER(:cp_filter1)' || CHR(10)
      || '        UNION' || CHR(10)
      || '        SELECT sn2.type_code    AS type_code' || CHR(10)
      || '              ,sn2.code_seq_id  AS code_seq_id' || CHR(10)
      || '        FROM   sde_bayer_code_sci_names_v sn2' || CHR(10)
      || '        WHERE  UPPER(sn2.short_name) like UPPER(:cp_filter1  || :cp_filter2)' || CHR(10)
So, DBMS_XMLGEN is faster, recommended, but doesn't allow for the specification of the encoding tag. DBMS_XMLQUERY allows for the encoding tag, as well as the specification of an id variable and value for each row in a rowset, but it cannot handle


 

 

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