Records from an Endnote library can be exported in a variety of file formats including: XML, and text based flat files such as tab delimited or other delimiter such as .csv (with some modification of the Endnote output style file). If I recall correctly, these file formats can be imported into MySQL. However, note that Endnote’s XML format is proprietary and might not be in a form that MySQL can successfully import. So you need to test the files.
Refer to the Help menu in the toolbar for information and instructions on exporting Endnote references in a variety of file formats. In the Search box type “import” in the search results click on “About Direct Export and Import Formats”.