SQL Server 2019

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DECLARE @json NVARCHAR(MAX)
 
SET @json = N'{"response":[{"partyId":"aa343434","prid":"88228822","partyName":"MyCompany",
              "addresses":[{"type":{"code":"1879539","description":"Operating Address"},"addressLine1":"Myaddress 4","addressLine2":"C/O xxx","addressLine3":"","addressLine4":"",
              "city":"yyy","state":{"code":"","description":""},"country":{"code":"1865641","description":"Denmark"},"postalCode":"2222","postalPlusCode":""}],
              "identifiers":[{"type":{"code":"1881600","description":"Bank IBAN"},"value":"888343434"},{"type":{"code":"1881591","description":"DUNS"},"value":"123456789"},{"type":{"code":"1881495","description":"NAT ID - DENMARK CVR NUMBER"},"value":"12345678"}],
              "sourceSystem":"source"},{"partyId":"aa343434","prid":"88228822","partyName":"MyNewCompany",
              "addresses":[{"type":{"code":"1879539","description":"Operating Address"},"addressLine1":"MyOtheraddress 23","addressLine2":"C/O zzz","addressLine3":"","addressLine4":"",
              "city":"zzz","state":{"code":"","description":""},"country":{"code":"1865641","description":"Denmark"},"postalCode":"3333","postalPlusCode":""}],
              "identifiers":[{"type":{"code":"1881591","description":"DUNS"},"value":"987654321"},{"type":{"code":"1881495","description":"NAT ID - DENMARK CVR NUMBER"},"value":"87654321"},
              {"type":{"code":"1881590","description":"CESID"},"value":"22334466"}],
              "sourceSystem":"source"}]}'

SELECT partyname, \addressLine1, addressLine2, city, country, postalcode, d.*
FROM OPENJSON(@json, 'strict $.response') 
WITH (
      partyName NVARCHAR(255),
      addresses NVARCHAR(MAX) AS JSON,
      identifiers NVARCHAR(MAX) AS JSON
     )
CROSS APPLY OPENJSON(addresses)
WITH (
      addressLine1 NVARCHAR(255),
      addressLine2 NVARCHAR(255),
      city NVARCHAR(255),
      country NVARCHAR(255) 'strict $.country.description',
      postalCode NVARCHAR(255)
     )
CROSS APPLY
    (SELECT MAX(CASE WHEN typecode = '1881591' THEN DUNS END) duns_1881591,
            MAX(CASE WHEN typecode = '1881495' THEN DUNS END) duns_1881495
     FROM OPENJSON(identifiers)
          WITH (typecode NVARCHAR(255) 'strict $.type.code',
                DUNS NVARCHAR(255) 'strict $.value'
               )
      WHERE typecode IN ( '1881591', '1881495')
     ) d

partyname	addressLine1	addressLine2	city	country	postalcode	duns_1881591	duns_1881495
MyCompany	0.0000	C/O xxx	yyy	Denmark	2222	123456789	12345678
MyNewCompany	0.0000	C/O zzz	zzz	Denmark	3333	987654321	87654321

Warning: Null value is eliminated by an aggregate or other SET operation.