Update multiple substrings within a string - sql-server

Question

I have a single text string stored in a SQL table which contains all of the text below. The format is XML but the field definition is varchar.
I am using SQL Server 2012 to query this data:
<?xml version="1.0" encoding="utf-16"?>
<SaveFileContext xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Mappings>
<SaveFileModel Header="Model1" FullPath="Model1" ViewType="ModelView" />
<SaveFileModel Header="xyz" FullPath="\\server\directory\" ViewType="TradeView" />
<SaveFileModel Header="Model2" FullPath="Model2" ViewType="ModelView" />
<SaveFileModel Header="Model3" FullPath="Model3" ViewType="ModelView" />
<SaveFileModel Header="abc" FullPath="\\server\directory\" ViewType="TradeView" />
<SaveFileModel Header="def" FullPath="\\server\directory\" ViewType="TradeView" />
<SaveFileModel Header="ghi" FullPath="\\server\directory\" ViewType="TradeView"/>
</Mappings>
</SaveFileContext>
How can I update or remove the entire lines of text where viewtype="ModelView"?
I want to remove any lines where viewtype="ModelView" within this single string and replace it with a blank space. In the example above I want to remove 3 lines total and leave the rest.
In the end I want the string to look like below (keep in mind all lines are contained in 1 single string. I just separated them to make viewing them easier.
<?xml version="1.0" encoding="utf-16"?>
<SaveFileContext xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Mappings>
<SaveFileModel Header="xyz" FullPath="\\server\directory\" ViewType="TradeView" />
<SaveFileModel Header="abc" FullPath="\\server\directory\" ViewType="TradeView" />
<SaveFileModel Header="def" FullPath="\\server\directory\" ViewType="TradeView" />
<SaveFileModel Header="ghi" FullPath="\\server\directory\" ViewType="TradeView"/>
</Mappings>
</SaveFileContext>
This is my current query that I am using to replace the lines but the values to replace are very specific. I'm basically entering the string to look for to replace.
IF OBJECT_ID('tempdb..#replacement') IS NOT NULL
DROP TABLE #replacement
CREATE TABLE #replacement (
string_pattern VARCHAR(100),
string_replacement VARCHAR(5)
);
INSERT INTO #replacement (
string_pattern,
string_replacement
)
VALUES
('<SaveFileModel Header="Model1" FullPath="Model1" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model2" FullPath="Model2" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model3" FullPath="Model3" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model4" FullPath="Model4" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model5" FullPath="Model5" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model6" FullPath="Model6" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model7" FullPath="Model7" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model8" FullPath="Model8" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model9" FullPath="Model9" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model10" FullPath="Model10" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model11" FullPath="Model11" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model12" FullPath="Model12" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model13" FullPath="Model13" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model14" FullPath="Model14" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model15" FullPath="Model15" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model16" FullPath="Model16" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model17" FullPath="Model17" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model18" FullPath="Model18" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model19" FullPath="Model19" ViewType="ModelView" />', ''),
('<SaveFileModel Header="Model20" FullPath="Model20" ViewType="ModelView" />', '');
DECLARE #string AS VARCHAR(MAX),
#userident varchar(20);
DECLARE userviewdef CURSOR FOR
SELECT
UserID
FROM
TableSettings where section = 'user view session'
OPEN userviewdef;
FETCH NEXT FROM userviewdef INTO
#userident;
WHILE ##FETCH_STATUS = 0
BEGIN
select #string = varcharvalue from tablesettings where section = 'user view session' and userid = #userident
-- Perform all replacements
SELECT #string = REPLACE(#string, string_pattern, string_replacement) FROM #replacement;
-- Return new string
--PRINT #string;
update tablesettings
set varcharvalue = #string
where section = 'user view session' and userid = #userident
FETCH NEXT FROM userviewdef INTO
#userident;
END;
CLOSE userviewdef;
DEALLOCATE userviewdef;
There are instances where a string could be what is seen below and it would not get removed since it doesn't fit any of the strings I coded to be removed. I want to find an easy way to remove any lines where ViewType="ModelView" since this is my criteria.
<SaveFileModel Header="ThisIsSomethingElse" FullPath="Model1" ViewType="ModelView" />
4/21/21:
After following the advice of #FrankPl to use XML here is what I came up with. The result returns a blank space. I might be coding the XML query piece incorrectly and need a bit of help:
DECLARE #stringXML XML,
#finalString varchar(max),
#userident varchar(20);
DECLARE userviewdef CURSOR FOR
SELECT
UserID
FROM
TableSettings where section = 'user view session';
OPEN userviewdef;
FETCH NEXT FROM userviewdef INTO
#userident;
WHILE ##FETCH_STATUS = 0
BEGIN
select #stringXML = varcharvalue from tablesettings where section = 'user view session' and userid = #userident
select #stringXML.query('
for $item in (/SaveFileContext/Mappings/SaveFileModel)
return if ($item[#ViewType = "ModelView"]) then string($item) else ""
')
select #finalString = convert(varchar(max), #stringXML)
-- Return new string
PRINT #finalstring;
FETCH NEXT FROM userviewdef INTO
#userident;
END;
CLOSE userviewdef;
DEALLOCATE userviewdef;

Answer 1

If you declare your #step variable as data type XML instead of varchar, you can use XQuery to process the data, in this case a FLOWR expression in curly braces within literal XML elements, the curly braces switch from literal mode to XPath mode:
SELECT #string.query('
<SaveFileContext>
<Mappings> {
for $item in (/SaveFileContext/Mappings/SaveFileModel)
return if ($item[#ViewType = "ModelView"]) then $item else ()
} </Mappings>
</SaveFileContext>
'
The XML declaration and the namespaces are swallowed by the SQLServer XML processor.
This solution assumes the data are valid XML fragments.
Please note that - as the whole query needs to be a SQL string (i. e. in single quotes), and XQuery accepts strings in double as well as in single quotes, for simplicity, I used double quotes here. Alternatively, I could have used doubled single quotes to escape them within the SQL string.