Sorting by one of many

Hi

Challenging sort problem for me. The rows can hold one to four dates and output 
should be sorted by only one. date1 being primary and if that is missing date2 
and so on. How can this be efficiently done?  


<root>
        <row>
                <name>A</name>
                <date2>20040101</date2>
        </row>
        <row>
                <name>C</name>
                <date3>20040103</date3>
                <date4>20040109</date4>
        </row>
        <row>
                <name>B</name>
                <date1>20040102</date1>
                <date3>20040101</date3>
        </row>
</root>


//matts