You need XQuery here. You can shred the XML into separate rows with .nodes
then use .value
to pull out the attribute values
SELECT
AccNum = x1.acc.value('@num' , 'int'),
Suffix = x1.acc.value('@suffix', 'int')
FROM YourTable t
CROSS APPLY t.xmlColumn.nodes('SAP/Accs/Acc') x1(acc);
If you also want the data from the SAP
root node then you can feed one .nodes
into another:
SELECT
AccNum = x2.acc.value('@num' , 'int'),
Suffix = x2.acc.value('@suffix', 'int'),
Post = x1.SAP.value('(Post/text())[1]', 'date'),
R = x1.SAP.value('(R/text())[1]', 'int')
FROM YourTable t
CROSS APPLY t.xmlColumn.nodes('SAP') x1(SAP)
CROSS APPLY x1.SAP.nodes('Accs/Acc') x2(acc);
db<>fiddle