I'm usint MS SQL and in XML field need update like this.
UPDATE Table
SET
IF (XMLdata.exist('/ns:root/Field/text()') = 0)
XMLdata.modify('
insert text{"New value"}
into (/ns:root/Field)[1]
')
ELSE
XMLdata.modify('
replace value of (/ns:root/Field/text())[1]
with "Replaced value"
'),
WHERE condition
Sample of 2 XML Files
Version 1
<ns:root ....>
<Field />
</ns:root>
Version 2
<ns:root ....>
<Field>Value</Field>
</ns:root>
I solved it.