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Q&A

How to get rid of HTML tags and convert entities in SQL Server?

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I have to migrate a bunch of text from an old application into a new one. Some of these texts contain HTML tags and entities (HTML editor was used) and now they do not want to support this in the new application.

How to get rid of the tags and transform the HTML entities?

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2 answers

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The best (ie non hacky) way to remove HTML tags is to load the text into a HTML parser and have it spit out the plain text version. There are plenty of HTML parsers out there, depending on your programming language, however, not SQL.

So in C# you'd read each entry in an external program, run it through the parser and write it back.

I'd suggest HtmlSanitiser to do this. Use it:

var sanitizer = new HtmlSanitizer(); PlainText = sanitizer.Sanitize(HtmlText);

the benefit of this is that you can remove specific tags from theHTML, leaving others. Eg you can leave i and b tags and remove everything else.

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One way is to create a scalar function that takes an NVARCHAR(MAX) input and performs the following operations:

  • replaces frequent tags with they plain text equivalent (e.g. <br> with chars 13 + 10)
  • replaces spacial entities with their correspondent UTF character (e.g. &copy; with ©)
  • completely remove tags and content in some cases (e.g. <style>)
-- Credit: https://stackoverflow.com/a/39532235/2780791
CREATE OR ALTER FUNCTION [dbo].[StripHTML]
--by Patrick Honorez --- www.idevlop.com
--inspired by http://stackoverflow.com/questions/457701/best-way-to-strip-html-tags-from-a-string-in-sql-server/39253602#39253602
(
	@HTMLText nvarchar(MAX)
)
RETURNS nvarchar(MAX)
AS
BEGIN
	DECLARE @Start  int
	DECLARE @End    int
	DECLARE @Length int

	set @HTMLText = replace(@htmlText, '<br>',CHAR(13) + CHAR(10))
	set @HTMLText = replace(@htmlText, '<br/>',CHAR(13) + CHAR(10))
	set @HTMLText = replace(@htmlText, '<br />',CHAR(13) + CHAR(10))
	set @HTMLText = replace(@htmlText, '<li>','- ')
	set @HTMLText = replace(@htmlText, '</li>',CHAR(13) + CHAR(10))

	set @HTMLText = replace(@htmlText, '&rsquo;' collate Latin1_General_CS_AS, ''''  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&quot;' collate Latin1_General_CS_AS, '"'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&amp;' collate Latin1_General_CS_AS, '&'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&euro;' collate Latin1_General_CS_AS, '€'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&lt;' collate Latin1_General_CS_AS, '<'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&gt;' collate Latin1_General_CS_AS, '>'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&oelig;' collate Latin1_General_CS_AS, 'oe'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&nbsp;' collate Latin1_General_CS_AS, ' '  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&copy;' collate Latin1_General_CS_AS, '©'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&laquo;' collate Latin1_General_CS_AS, '«'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&reg;' collate Latin1_General_CS_AS, '®'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&plusmn;' collate Latin1_General_CS_AS, '±'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&sup2;' collate Latin1_General_CS_AS, '²'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&sup3;' collate Latin1_General_CS_AS, '³'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&micro;' collate Latin1_General_CS_AS, 'µ'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&middot;' collate Latin1_General_CS_AS, '·'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ordm;' collate Latin1_General_CS_AS, 'º'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&raquo;' collate Latin1_General_CS_AS, '»'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&frac14;' collate Latin1_General_CS_AS, '¼'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&frac12;' collate Latin1_General_CS_AS, '½'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&frac34;' collate Latin1_General_CS_AS, '¾'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&Aelig' collate Latin1_General_CS_AS, 'Æ'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&Ccedil;' collate Latin1_General_CS_AS, 'Ç'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&Egrave;' collate Latin1_General_CS_AS, 'È'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&Eacute;' collate Latin1_General_CS_AS, 'É'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&Ecirc;' collate Latin1_General_CS_AS, 'Ê'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&Ouml;' collate Latin1_General_CS_AS, 'Ö'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&agrave;' collate Latin1_General_CS_AS, 'à'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&acirc;' collate Latin1_General_CS_AS, 'â'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&auml;' collate Latin1_General_CS_AS, 'ä'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&aelig;' collate Latin1_General_CS_AS, 'æ'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ccedil;' collate Latin1_General_CS_AS, 'ç'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&egrave;' collate Latin1_General_CS_AS, 'è'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&eacute;' collate Latin1_General_CS_AS, 'é'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ecirc;' collate Latin1_General_CS_AS, 'ê'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&euml;' collate Latin1_General_CS_AS, 'ë'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&icirc;' collate Latin1_General_CS_AS, 'î'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ocirc;' collate Latin1_General_CS_AS, 'ô'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ouml;' collate Latin1_General_CS_AS, 'ö'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&divide;' collate Latin1_General_CS_AS, '÷'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&oslash;' collate Latin1_General_CS_AS, 'ø'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ugrave;' collate Latin1_General_CS_AS, 'ù'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&uacute;' collate Latin1_General_CS_AS, 'ú'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ucirc;' collate Latin1_General_CS_AS, 'û'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&uuml;' collate Latin1_General_CS_AS, 'ü'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&quot;' collate Latin1_General_CS_AS, '"'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&amp;' collate Latin1_General_CS_AS, '&'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&mdash;' collate Latin1_General_CS_AS, '—'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ndash;' collate Latin1_General_CS_AS, '–'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&bull;' collate Latin1_General_CS_AS, '•'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&trade;' collate Latin1_General_CS_AS, '™'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&rdquo;' collate Latin1_General_CS_AS, '"'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&lsquo;' collate Latin1_General_CS_AS, ''''  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&ldquo;' collate Latin1_General_CS_AS, ''''  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&oacute;' collate Latin1_General_CS_AS, 'ó'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&deg;' collate Latin1_General_CS_AS, '°'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&hellip;' collate Latin1_General_CS_AS, '…'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&atilde;' collate Latin1_General_CS_AS, 'ã'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&lrm;' collate Latin1_General_CS_AS, '•'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&iuml;' collate Latin1_General_CS_AS, 'ï'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&rarr;' collate Latin1_General_CS_AS, '→'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&bdquo;' collate Latin1_General_CS_AS, '"'  collate Latin1_General_CS_AS)

	-- Remove anything between <STYLE> tags
	SET @Start = CHARINDEX('<STYLE', @HTMLText)
	SET @End = CHARINDEX('</STYLE>', @HTMLText, CHARINDEX('<', @HTMLText)) + 7
	SET @Length = (@End - @Start) + 1

	WHILE (@Start > 0 AND @End > 0 AND @Length > 0) BEGIN
	SET @HTMLText = STUFF(@HTMLText, @Start, @Length, '')
	SET @Start = CHARINDEX('<STYLE', @HTMLText)
	SET @End = CHARINDEX('</STYLE>', @HTMLText, CHARINDEX('</STYLE>', @HTMLText)) + 7
	SET @Length = (@End - @Start) + 1
	END

	-- Remove anything between <whatever> tags
	SET @Start = CHARINDEX('<', @HTMLText)
	SET @End = CHARINDEX('>', @HTMLText, CHARINDEX('<', @HTMLText))
	SET @Length = (@End - @Start) + 1

	WHILE (@Start > 0 AND @End > 0 AND @Length > 0) BEGIN
	SET @HTMLText = STUFF(@HTMLText, @Start, @Length, '')
	SET @Start = CHARINDEX('<', @HTMLText)
	SET @End = CHARINDEX('>', @HTMLText, CHARINDEX('<', @HTMLText))
	SET @Length = (@End - @Start) + 1
	END

	set @HTMLText = replace(@htmlText, '&lsaquo;' collate Latin1_General_CS_AS, '<'  collate Latin1_General_CS_AS)
	set @HTMLText = replace(@htmlText, '&rsaquo;' collate Latin1_General_CS_AS, '>'  collate Latin1_General_CS_AS)

	RETURN LTRIM(RTRIM(@HTMLText))

END


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