Unable to fetch data using extractvalue function - sql

Question

I have a table having a XML Type column in Oracle DB. I am trying to use the extractvalue and updatexml functions on that table.
XML
<?xml version = '1.0' encoding = 'UTF-8'?>
<custominfo>
<singlerecord ZIP="51100"/>
<multiplerecord type="ONE_TIME_CHARGES_LIST">
<record DESCRIPTION="Device Payment" RATE="1000000" TAX="0"/>
<record DESCRIPTION="Plan Payment" RATE="480000" TAX="0"/>
<record DESCRIPTION="Deposit" RATE="1000000" TAX="0"/>
</multiplerecord>
</custominfo>
Query
select EXTRACTVALUE(XMLCONTENT,'//record[#DESCRIPTION="Plan Payment"]') from TABLE_XML X;
Can anyone suggest what I am doing wrong here?
After sorting out the extract I want to replace the DESCRIPTION from "Plan Payment" to "Pre Plan Payment".

Answer 1

What you are doing is working - it's giving you the text value of the record node with that attribute value. But that node is empty:
<record DESCRIPTION="Plan Payment" RATE="480000" TAX="0"/>
has three attributes but the node itself has no content - it's an empty tag. So your query is returning null, which is correct. If you wanted to see that you'd found the node you could get an attribute value instead:
select EXTRACTVALUE(XMLCONTENT,'//record[#DESCRIPTION="Plan Payment"]/#DESCRIPTION')
from TABLE_XML X;
However, the extractvalue() function has long been deprecated, so you shouldn't really be using it anyway.
You can use an XMLQuery to view the whole matching record node; as the node has no content there isn't much point in getting its content, as your current query does:
select XMLQuery('$x//record[#DESCRIPTION="Plan Payment"]'
passing xmlcontent as "x"
returning content
) as result
from table_xml;
RESULT
--------------------------------------------------------------------------------
<record DESCRIPTION="Plan Payment" RATE="480000" TAX="0"/>
The updatexml() function is deprecated as well. You can use an XMLQuery to modify the attribute name too:
select XMLQuery('copy $i := $x modify
(for $j in $i//record[#DESCRIPTION="Plan Payment"]/#DESCRIPTION
return replace value of node $j with $r)
return $i'
passing xmlcontent as "x", 'Pre Plan Payment' as "r"
returning content
) as result
from table_xml;
Using a CTE for your sample XML document, and wrapping it in an XMLSerialize call to retain the formatting for readability:
with table_xml (xmlcontent) as (
select xmltype(q'[<?xml version = '1.0' encoding = 'UTF-8'?>
<custominfo>
<singlerecord ZIP="51100"/>
<multiplerecord type="ONE_TIME_CHARGES_LIST">
<record DESCRIPTION="Device Payment" RATE="1000000" TAX="0"/>
<record DESCRIPTION="Plan Payment" RATE="480000" TAX="0"/>
<record DESCRIPTION="Deposit" RATE="1000000" TAX="0"/>
</multiplerecord>
</custominfo>]'
) from dual
)
select XMLSerialize(
document
XMLQuery('copy $i := $x modify
(for $j in $i//record[#DESCRIPTION="Plan Payment"]/#DESCRIPTION
return replace value of node $j with $r)
return $i'
passing xmlcontent as "x", 'Pre Plan Payment' as "r"
returning content
)
indent
) as result
from table_xml;
RESULT
--------------------------------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<custominfo>
<singlerecord ZIP="51100"/>
<multiplerecord type="ONE_TIME_CHARGES_LIST">
<record DESCRIPTION="Device Payment" RATE="1000000" TAX="0"/>
<record DESCRIPTION="Pre Plan Payment" RATE="480000" TAX="0"/>
<record DESCRIPTION="Deposit" RATE="1000000" TAX="0"/>
</multiplerecord>
</custominfo>
If you want to update the value in the table you can use the same query as part of an update statement, filtered on rows that match. Read more.