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SQL PUZZLE | The Child XML Node Puzzle | SQL Interview Question

There are two table here names Parents and TheChildren. In this puzzle you have to generate the XML using T-SQL, the catch here is that if any parent didn’t have any children then for that parent do not show the children node. Please see the sample input and expected output.

Sample Input

Parents

Id Vals
2 Pawan
1 Avtaar

TheChildren

ChildId ParentId ChildName
1 2 Avika

Expected Output

--

<Families>
  <Parent>
    <ParentName>Pawan</ParentName>
    <Chilren>
      <Childs>
        <ChildName>Avika</ChildName>
      </Childs>
    </Chilren>
  </Parent>
  <Parent>
    <ParentName>Avtaar</ParentName>
  </Parent>
</Families>

--

Script – DDL and INSERT Sample Data

--

CREATE TABLE Parents
(
	  Id INT
	, Nm VARCHAR(10)
)
GO

INSERT INTO Parents VALUES
(2,'Pawan'),
(1,'Avtaar')
GO

CREATE TABLE TheChildren
(
	  ChildId INT
	, ParentId INT
	, ChildName VARCHAR(10)
)
GO

INSERT INTO TheChildren VALUES
(1,2,'Avika')
GO

SELECT * FROM Parents
GO

SELECT * FROM TheChildren
GO

--

SOLUTION – 1

--

SELECT
(
    SELECT p.Nm ParentName,
    (
        SELECT c.ChildName
        FROM   TheChildren c
        WHERE  p.Id = c.ParentId
        FOR XML PATH('Childs'),TYPE
    ) AS Chilren
    FROM Parents P
    FOR XML PATH('Parent'), TYPE
) FOR XML PATH('Families')
GO

--

Output – 1

--

<Families>
  <Parent>
    <ParentName>Pawan</ParentName>
    <Chilren>
      <Childs>
        <ChildName>Avika</ChildName>
      </Childs>
    </Chilren>
  </Parent>
  <Parent>
    <ParentName>Avtaar</ParentName>
  </Parent>
</Families>

--

Enjoy 🙂

Please add comment(s) if you have one or multiple solutions in mind. Thank You.

Pawan Khowal

Pawan is a SQL Server Developer. If you need any help in writing code/puzzle or training please email at – pawankkmr”AT”gmail.com. Meanwhile please go throgh the top pages from his blog.

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