Selecting from and inserting to complex Oracle XMLTYPE data

Question

I've written simple Oracle queries to extract XMLTYPE data before, but this XML is different - I need to pull information from attributes, child elements, and their respective attributes. I also would like to write an INSERT statement as well (preferably one that is able to find the highest option value and add 1). Consider the following XML:

<metadata>
    <fields>
        <field name="cusInt01" label="Reference point">
            <option value="1">CB</option>
            <option value="2">CF</option>
            <option value="3">DF</option>
            <option value="4">EKB</option>
            <option value="5">ES</option>
            <option value="6">GL</option>
            <option value="7">GR</option>
            <option value="8">KB</option>
            <option value="9">KBE</option>
            <option value="10">MSL</option>
            <option value="11">PT</option>
            <option value="12">RB</option>
            <option value="13">RF</option>
            <option value="14">RT</option>
            <option value="15">UN</option>
            <option value="16">UNK</option>
        </field>
    </fields>
</metadata>

I can write, for instance, a query to extract all of the field names:

select 
  field_names.*
FROM
  metadata m,
  XMLTABLE('/metadata/fields/field'
       PASSING xmltype(m.xml_string)
       COLUMNS field_name VARCHAR(32) PATH '@name') field_names;

How do I write a query that can extract all the different information in a tabular form? How do I, for instance, display it as:

field_name   |   field_label       |   option_value   |   option_label
cusInt01         Reference point       1                  CB
cusInt01         Reference point       2                  CF
cusInt01         Reference point       2                  DF

... etc. Thoughts? I've been trying to cobble a query together but so far spinning my wheels.

Answer 1

In your example, the data is at multiple levels. Each field can have many option. So, you must break up field as well as option elements with XMLTable. First, you should break field elements, where option elements are mapped as XMLType. Then pass it to second XMLTable to further break it down.

Data Setup:

CREATE TABLE metadata (xml_string VARCHAR2 (2000));

INSERT INTO metadata
     VALUES ('<metadata>
    <fields>
        <field name="cusInt01" label="Reference point">
            <option value="1">CB</option>
            <option value="2">CF</option>
            <option value="3">DF</option>
            <option value="4">EKB</option>
            <option value="5">ES</option>
            <option value="6">GL</option>
            <option value="7">GR</option>
            <option value="8">KB</option>
            <option value="9">KBE</option>
            <option value="10">MSL</option>
            <option value="11">PT</option>
            <option value="12">RB</option>
            <option value="13">RF</option>
            <option value="14">RT</option>
            <option value="15">UN</option>
            <option value="16">UNK</option>
        </field>
    </fields>
</metadata>');

COMMIT;

Query:

SELECT field.field_name,
       field.field_label,
       options.option_value,
       options.option_label
  FROM metadata m,
       XMLTABLE (
          'metadata/fields/field'
          PASSING xmltype (m.xml_string)
          COLUMNS field_name VARCHAR2 (32) PATH '@name',
                  field_label VARCHAR2 (32) PATH '@label',
                  field_options XMLTYPE PATH 'option') field,
       XMLTABLE (
          'option'
          PASSING field.field_options
          COLUMNS option_value NUMBER PATH '@value',
                  option_label VARCHAR2 (10) PATH '/') options;

Result:

FIELD_NAME    FIELD_LABEL        OPTION_VALUE    OPTION_LABEL
-------------------------------------------------------------
cusInt01      Reference point    1               CB           
cusInt01      Reference point    2               CF           
cusInt01      Reference point    3               DF           
cusInt01      Reference point    4               EKB          
cusInt01      Reference point    5               ES           
cusInt01      Reference point    6               GL           
cusInt01      Reference point    7               GR           
cusInt01      Reference point    8               KB           
cusInt01      Reference point    9               KBE          
cusInt01      Reference point    10              MSL          
cusInt01      Reference point    11              PT           
cusInt01      Reference point    12              RB           
cusInt01      Reference point    13              RF           
cusInt01      Reference point    14              RT           
cusInt01      Reference point    15              UN           
cusInt01      Reference point    16              UNK 

Similar example at Oracle XML DB Developer's Guide.