Updating Node structure in SQL XML data - sql

Question

I have some Data stored as XML in SQL Server that looks as follows:
<FormSearchFilter>
.......
<IDs>
<int>1</int>
<int>2</int>
</IDs>
.......
</FormSearchFilter>
This XML is mapped to a DTO and the data type for IDs is changing from a List to a string. As a result I now need to updae all existing XML: data to look as follows:
<FormSearchFilter>
.......
<IDs>1,2</IDs>
.......
</FormSearchFilter>
Whats the best way to achieve this via an update query

Answer 1

Besides the hint, that this is a very bad idea! you might try something like this:
DECLARE #t TABLE(
Id INT NOT NULL IDENTITY(1,1),
xml XML)
INSERT INTO #t(xml)
VALUES
('<FormSearchFilter><IDs><int>1</int><int>2</int></IDs></FormSearchFilter>'),
('<FormSearchFilter><IDs><int>1</int><int>2</int><int>3</int></IDs></FormSearchFilter>'),
('<FormSearchFilter><IDs><int>1</int><int>2</int><int>3</int><int>4</int></IDs></FormSearchFilter>');
UPDATE #t
SET [xml]= (SELECT REPLACE([xml].query('data(/FormSearchFilter/IDs/int)').value('.','nvarchar(max)'),' ',',') AS IDs
FOR XML PATH('FormSearchFilter'));
SELECT * FROM #t
Explanation:
XQuery function data() will return alle text() nodes (in your case the int values) separated by a blank. This can be replaced with a comma to get the list needed.
UPDATE: Preserve other elements (be aware, that the order changes)
INSERT INTO #t(xml)
VALUES
('<FormSearchFilter><test>x</test><IDs><int>1</int><int>2</int></IDs></FormSearchFilter>'),
('<FormSearchFilter><IDs><int>1</int><int>2</int><int>3</int></IDs><test>x</test></FormSearchFilter>'),
('<FormSearchFilter><IDs><int>1</int><int>2</int><int>3</int><int>4</int></IDs></FormSearchFilter>');
UPDATE #t
SET [xml]= (SELECT [xml].query('/FormSearchFilter/*[local-name()!="IDs"]') AS [*]
,REPLACE([xml].query('data(/FormSearchFilter/IDs/int)').value('.','nvarchar(max)'),' ',',') AS IDs
FOR XML PATH('FormSearchFilter'));
SELECT * FROM #t

Answer 2

A bit of a hack, and if you're open to a helper Table-Valued Function.
Example
Declare #XML xml = '
<FormSearchFilter>
<OtherContent>Some Content</OtherContent>
<IDs>
<int>1</int>
<int>2</int>
</IDs>
<IDs>
<int>11</int>
<int>12</int>
<int>13</int>
</IDs>
<IDs>
<int>99</int>
</IDs>
<MoreContent>Some MORE Content</MoreContent>
</FormSearchFilter>
'
Select #XML = replace(cast(#XML as varchar(max)),RetVal,NewVal)
From (
Select *
,NewVal = stuff(replace(replace(RetVal,'<int>',','),'</int>',''),1,1,'')
From [dbo].[tvf-Str-Extract](cast(#XML as varchar(max)),'<IDs>','</IDs>')
) A
Select #XML
Returns
<FormSearchFilter>
<OtherContent>Some Content</OtherContent>
<IDs>1,2</IDs>
<IDs>11,12,13</IDs>
<IDs>99</IDs>
<MoreContent>Some MORE Content</MoreContent>
</FormSearchFilter>
The TVF was created because I tired of extracting content (left,right,charindex,patindex,reverse,...). It is a modifed parse/split function which accepts two non-like delimiters. Just to illustrate, if you were to run:
Select * From [dbo].[tvf-Str-Extract](cast(#XML as varchar(max)),'<IDs>','</IDs>')
The results would be
RetSeq RetPos RetVal
1 65 <int>1</int><int>2</int>
2 100 <int>11</int><int>12</int><int>13</int>
3 150 <int>99</int>
The TVF if Interested
CREATE FUNCTION [dbo].[tvf-Str-Extract] (#String varchar(max),#Delimiter1 varchar(100),#Delimiter2 varchar(100))
Returns Table
As
Return (
with cte1(N) As (Select 1 From (Values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N(N)),
cte2(N) As (Select Top (IsNull(DataLength(#String),0)) Row_Number() over (Order By (Select NULL)) From (Select N=1 From cte1 N1,cte1 N2,cte1 N3,cte1 N4,cte1 N5,cte1 N6) A ),
cte3(N) As (Select 1 Union All Select t.N+DataLength(#Delimiter1) From cte2 t Where Substring(#String,t.N,DataLength(#Delimiter1)) = #Delimiter1),
cte4(N,L) As (Select S.N,IsNull(NullIf(CharIndex(#Delimiter1,#String,s.N),0)-S.N,8000) From cte3 S)
Select RetSeq = Row_Number() over (Order By N)
,RetPos = N
,RetVal = left(RetVal,charindex(#Delimiter2,RetVal)-1)
From (
Select *,RetVal = Substring(#String, N, L)
From cte4
) A
Where charindex(#Delimiter2,RetVal)>1
)
/*
Max Length of String 1MM characters
Declare #String varchar(max) = 'Dear [[FirstName]] [[LastName]], ...'
Select * From [dbo].[tvf-Str-Extract] (#String,'[[',']]')
*/

Answer 3

Not particularly elegant but does end up with the required output:
DECLARE #t TABLE(
Id INT NOT NULL IDENTITY(1,1),
xml XML)
INSERT INTO #t(xml)
VALUES
('<FormSearchFilter><IDs><int>1</int><int>2</int></IDs></FormSearchFilter>'),
('<FormSearchFilter><IDs><int>1</int><int>2</int><int>3</int></IDs></FormSearchFilter>'),
('<FormSearchFilter><IDs><int>1</int><int>2</int><int>3</int><int>4</int></IDs></FormSearchFilter>');
DECLARE #updates TABLE(
Id INT,
UpdatedValue XML
)
INSERT INTO #updates
SELECT
Id,
(SELECT STUFF((
SELECT
',' + c.value('.', 'varchar')
FROM #t t1
CROSS APPLY t1.xml.nodes('//IDs/int') x(c)
WHERE t1.Id = t.Id
FOR XML PATH('')
), 1, 1, '') IDs
FOR XML PATH(''))
FROM #t t
-- remove existing IDs node
UPDATE #t
SET xml.modify('delete //IDs')
-- insert updated IDs node back in
UPDATE t
SET xml.modify('insert sql:column("u.UpdatedValue") into (/FormSearchFilter)[1]')
FROM #t t
JOIN #updates u ON t.Id = u.Id