PostgreSQL extract multi value from xml and into columns - postgresql

Question

I have the below XML in each row with different data.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:Declaration xmlns="urn:wco:datamodel:WCO:Declaration_DS:DMS:2" xmlns:ns2="urn:wco:datamodel:WCO:DEC-DMS:2" xmlns:ns3="urn:wco:datamodel:WCO:WCO_DEC_EDS_AUTHORISATION:1">
<ns2:FunctionCode>9</ns2:FunctionCode>
<ns2:ProcedureCategory>B1</ns2:ProcedureCategory>
<ns2:FunctionalReferenceID>LRNU4YZHFFG</ns2:FunctionalReferenceID>
<ns2:IssueDateTime>
<DateTimeString formatCode="304">20210816084322+01</DateTimeString>
</ns2:IssueDateTime>
<ns2:TypeCode>EXA</ns2:TypeCode>
<ns2:GoodsItemQuantity>2</ns2:GoodsItemQuantity>
<ns2:DeclarationOfficeID>ABCd</ns2:DeclarationOfficeID>
<ns2:TotalGrossMassMeasure unitCode="KGM">33000.000</ns2:TotalGrossMassMeasure>
<ns2:TotalPackageQuantity>400</ns2:TotalPackageQuantity>
<ns2:Submitter>
<ns2:Name>ABC</ns2:Name>
<ns2:ID>ABC</ns2:ID>
</ns2:Submitter>
</ns2:Declaration>
ID
messagebody
1
<Xml...
2
<Xml...
what I would like to have is a query that extracts some elements from the XML and put them in a table as below
ID
messagebody
FunctionalReferenceID
ProcedureCategory
1
<Xml...
LRR....
B1
2
<Xml...
LR1....
B2
I'm using the below sql to extract only 1 path
select u.val::text
from sw_customs_message scm
cross join unnest(xpath('//ns2:ProcedureCategory/text()',
scm.messagebody::xml,
array[array['ns2','urn:wco:datamodel:WCO:DEC-DMS:2']])) as u(val)
where u.val::text = 'H7'
How i can use the xmltable() ?

Answer 1

Using xmltable() is typically easier for multiple columns (and rows), especially if namespaces come into play:
select scm.id, mb.*
from sw_customs_message scm
cross join xmltable(xmlnamespaces ('urn:wco:datamodel:WCO:DEC-DMS:2' as ns2,
'urn:wco:datamodel:WCO:WCO_DEC_EDS_AUTHORISATION:1' as ns3),
'/ns2:Declaration'
passing cast(messagebody as xml)
columns
functional_reference_id text path 'ns2:FunctionalReferenceID',
procedure_category text path 'ns2:ProcedureCategory',
function_code int path 'ns2:FunctionCode',
good_items_quantity int path 'ns2:GoodsItemQuantity'
) as mb
where mb.procedure_category = ...
messagebody should really be defined as xml so that you don't need to cast it each time you want to do something with the XML.