How to delete duplicate XML data with specific attribute - sql

Question

I have this SQL query
SELECT r.Address.value('(//City)[1]','VARCHAR(MAX)') "City/#Title" ,
(SELECT r1.FirstName , r1.SecondName
FROM Reader r1
where r.Address.value('(//City)[1]','VARCHAR(MAX)') = r1.Address.value('(//City)[1]','VARCHAR(MAX)')
FOR XML RAW('Reader'),TYPE) AS "City/Readers"
FROM Reader r
FOR XML PATH(''),ROOT('Cities');
This query produces such data:
<Cities>
<City Title="New York">
<Readers>
<Reader FirstName="JON" SecondName="SHOW" />
<Reader FirstName="Poll" SecondName="Aeron" />
</Readers>
</City>
<City Title="New York">
<Readers>
<Reader FirstName="JON" SecondName="SHOW" />
<Reader FirstName="Poll" SecondName="Aeron" />
</Readers>
</City>
<City Title="Kharkiv">
<Readers>
<Reader FirstName="Slavik" SecondName="Romanov" />
</Readers>
</City>
<City Title="Boca Juniors">
<Readers>
<Reader FirstName="Julio " SecondName="Pedro" />
</Readers>
</City>
<City Title="London">
<Readers>
<Reader FirstName="Johnny " SecondName="Smith" />
</Readers>
</City>
</Cities>
I want to delete duplicate elements, exactly the second node.
The query must generate data without the duplicates

Answer 1

Selecting distinct City before constructing the XML would be more efficient. This is one possible way using Common Table Expression (CTE) :
;WITH Cities
AS(
SELECT DISTINCT r.Address.value('(//City)[1]','VARCHAR(MAX)') As City
FROM Reader r
)
SELECT
c.City "City/#Title",
(SELECT r1.FirstName , r1.SecondName
FROM Reader r1
where c.City = r1.Address.value('(//City)[1]','VARCHAR(MAX)')
FOR XML RAW('Reader'),TYPE) AS "City/Readers"
FROM Cities c
FOR XML PATH(''),ROOT('Cities');
Fiddle Demo