DB2 importing/replacing fields from a file that contains XML
Why don't you just 

update table2 set column_xml2 = 
(select column_xml from table1 where &lt;predicate clause&gt;) where &lt;predicate clause&gt;;


?

With CLOBs you pretty much have to do that. You can only update the entire CLOB. Now if are on DB2 9.1 or higher, you could store these in a field of type XML and then you could attempt to update specific XML elements like how you are hoping to do.