Unlocking Hidden Data: Extracting XML from ZIP/RAR Compressed VARBINARY in SQL Server

Are you tired of feeling like you’re stuck between a rock and a hard place, unable to access valuable data buried deep within a ZIP or RAR compressed file saved as a VARBINARY in your SQL Server database? Fear not, dear developer, for today we embark on a thrilling adventure to extract that elusive XML data and shine a light on the mysteries within!

Prerequisites and Assumptions

Before we dive into the meat of the matter, let’s establish some ground rules. For this tutorial, we’ll assume you have:

• A SQL Server database with a table containing a VARBINARY column storing compressed XML data in ZIP or RAR format.
• A basic understanding of SQL Server and XML data types.
• SQL Server Management Studio (SSMS) or a similar tool for executing queries.

The Challenge: Working with Compressed Data

When dealing with compressed data, the biggest hurdle is deciphering the encoded information. SQL Server’s built-in functions can’t directly access the contents of a ZIP or RAR file. We need to employ some creative problem-solving to extract the XML data.

Step 1: Decompressing the VARBINARY Data

To begin, we’ll use the OPENROWSET function in conjunction with the BULK option to read the VARBINARY data into aTemporary table. This will enable us to work with the decompressed data.

DECLARE @compressed_data VARBINARY(MAX);
SET @compressed_data = (SELECT compressed_xml_data FROM your_table WHERE id = 1);

DECLARE @temp_table TABLE (decompressed_data VARBINARY(MAX));
INSERT INTO @temp_table
SELECT CAST('' AS XML).value('xs:base64Binary(decompress(@compressed_data))', 'VARBINARY(MAX)');

SELECT * FROM @temp_table;

Step 2: Unzipping/RARing the Decompressed Data

Now that we have the decompressed data, we need to extract the XML from the ZIP or RAR file. We’ll utilize the master.dbo.xp_dirtree extended stored procedure to create a temporary directory and extract the contents of the compressed file.

DECLARE @temp_dir SYSNAME = 'C:\Temp\unzip';
EXEC master.dbo.xp_create_subdir @temp_dir;

DECLARE @unzip_query NVARCHAR(MAX);
SET @unzip_query = 'xp_cmdshell ''powershell -Command "Expand-Archive -Path ''' + @temp_dir + '\' + 'compressed_file.zip' + ''' -DestinationPath ''' + @temp_dir + '''"'')';

EXEC sp_executesql @unzip_query;

Step 3: Reading the XML File

With the XML file now extracted to a temporary directory, we can read its contents using the OPENROWSET function again, this time with the BULK option.

DECLARE @xml_data XML;
SET @xml_data = (SELECT CONVERT(XML, BulkColumn) FROM OPENROWSET(BULK ''' + @temp_dir + '\' + 'xml_file.xml', SINGLE_CLOB) AS Data);

SELECT @xml_data;

Troubleshooting and Variations

As with any complex operation, issues may arise. Be prepared to encounter the following obstacles:

• Permissions**: Ensure the SQL Server service account has read and write access to the temporary directory.
• File Paths**: Verify the file paths used in the script are correct and adjust accordingly.
• ZIP/RAR Passwords**: If the compressed file is password-protected, you’ll need to modify the PowerShell script to include the password.
• Large Files**: Be mindful of file size limits and adjust the script as needed to accommodate larger files.

RAR vs. ZIP: What’s the Difference?

While both ZIP and RAR are popular compression formats, they differ in their compression algorithms and compatibility. RAR, developed by WinRAR, offers better compression ratios and supports more features, but ZIP is more widely adopted and compatible with a broader range of tools. When working with RAR files, you may need to install the WinRAR command-line tool (rar.exe) and modify the PowerShell script accordingly.

Format	Compression Ratio	Compatibility
ZIP	Good	High
RAR	Excellent	Medium

Conclusion

With these steps, you’ve successfully extracted XML data from a ZIP or RAR compressed file stored as a VARBINARY in your SQL Server database. Pat yourself on the back, dear developer! You’ve overcome the challenges and unlocked the secrets hidden within.

Remember to adapt this script to your specific requirements, and don’t hesitate to explore further optimizations and variations to tackle the unique complexities of your data.

Bonus: SQL Server 2017 and Beyond

For those fortunate enough to be working with SQL Server 2017 or later, you can leverage the COMPRESS and DECOMPRESS functions to simplify the process. Take a look at the following example:

DECLARE @compressed_data VARBINARY(MAX);
SET @compressed_data = (SELECT compressed_xml_data FROM your_table WHERE id = 1);

DECLARE @decompressed_data VARBINARY(MAX);
SET @decompressed_data = DECOMPRESS(@compressed_data);

SELECT CONVERT(XML, @decompressed_data);

Life just got a whole lot easier, didn’t it?

Now, go forth and conquer the realm of compressed data in SQL Server!

Frequently Asked Question

Get ready to uncompress the confusions around XML compressed in ZIP/RAR files saved as VARBINARY in SQL Server!