If you are using MySQL data saving and seeing this error, it means your server is missing MySQLoo9. Most hosts have the module automatically install through their control panel, so check there first. If not, you can download and install it directly from this link: https://github.com/FredyH/MySQLOO/releases
Install it by putting it in the following directory: garrysmod/lua/bin
If it does not exist, just create that directory.