I have had some comments on my stored functions for XML output from MySql. First of all, publishning the code as a part of a blog post was not a good choice. All xml chars, like < and > must be escaped, and I missed some. I should probably have used the xml_escape function to precess my text...
That is fixed now, and also I have put the function definitions on the MySql forge, here. Please do not hesitate to tell me if you find any errors, or have suggestions for improvement.
Another comment was about the xml functionality of 'mysql --xml'. Yes, there is a function for generating xml output from MySql, I do know that. But if you need to output xml from your application there are a number of problems with it:
1) it has to be invoked from the command line, so you need to start a command shell, redirect output somewhere etc. This is not always possible and might not be a good alternative even if it is.
2) you have no control over the xml format, you would probably need to add som XSL processing to get the format you need. This will make it complicated, and XSL knowledge is not that common.
So, there are a number of situations where the 'mysql --xml' approach is not very suitable, but the stored function might do the job. But certainly you should consider the 'mysql --xml' possibility before choosing.