Generating XML Files with FOR XML PATH
By Tom Nonmacher
XML, or Extensible Markup Language, is a powerful tool for storing and transporting data. In the world of database management, it's often necessary to generate XML files from SQL Server data. SQL Server 2016 and 2017, MySQL 5.7, DB2 11.1, and Azure SQL have built-in capabilities to generate XML files using the FOR XML PATH statement. This article will walk you through how to generate XML data using the FOR XML PATH statement in these technologies.
The FOR XML PATH statement is a highly versatile feature in SQL Server 2016 and 2017. It allows you to format your query results as XML, and thus generate XML files. Here's a basic example of how to use it:
SELECT Column1, Column2
FROM YourTable
FOR XML PATH('YourElement'), ROOT('YourRootElement')
In this example, 'YourTable' is the name of your table, 'Column1' and 'Column2' are the names of the columns you wish to include in your XML data, 'YourElement' is the name of the XML element that will contain the column data, and 'YourRootElement' is the root element of your XML data. You can replace these with the appropriate names for your use case.
MySQL 5.7 doesn't have a built-in FOR XML PATH function like SQL Server, but you can achieve similar results using CONCAT and GROUP_CONCAT functions. Here's an example:
SELECT CONCAT('<YourRootElement>',
GROUP_CONCAT('<YourElement>', Column1, '</YourElement>'),'</YourRootElement>') AS 'XML'
FROM YourTable;
In the above example, 'YourTable' is the name of your table, 'Column1' is the name of the column you wish to include in your XML data, and 'YourElement' and 'YourRootElement' are the names of your XML elements. The CONCAT function concatenates the XML tags with the column data, and the GROUP_CONCAT function combines all rows of the result into a single string.
DB2 11.1 has a built-in XMLAGG function which can be used to generate XML data. Here's an example:
SELECT XML2CLOB(XMLAGG(XMLELEMENT(NAME "YourElement", Column1))) AS "XML"
FROM YourTable;
In this example, 'YourTable' is the name of your table, 'Column1' is the name of the column you wish to include in your XML data, and 'YourElement' is the name of your XML element. The XMLELEMENT function creates an XML element with the specified name and content, and the XMLAGG function aggregates all the XML elements into a single XML document.
Azure SQL, being a cloud-based version of SQL Server, also supports the FOR XML PATH statement. The usage is identical to that in SQL Server 2016 and 2017. This feature makes it easy to generate XML data in the cloud, which can then be downloaded or sent to other cloud services.
In conclusion, generating XML data from SQL Server, MySQL, DB2, and Azure SQL data is a straightforward process thanks to the built-in capabilities of these technologies. Whether you're working with on-premises databases or cloud-based databases, you can easily generate XML files to store and transport your data.