You need to tell the game you are UPDATING a data entry that has already been set elsewhere, and you need to ensure you are using the correct table name that needs updating (in this case, "Resources" table). Using "<row>" is only for adding a whole new data set (or row) to a table.
<Where Type="RESOURCE_IVORY" />
<Set Happiness="1" />
Don't forget you also need to edit the "Actions" of your project. You need action set "OnModActivated", type "UpdateDatabase", and value needs to match the name and relative path of whatever xml file you created (eg "mynewresources.xml" if your mod's XML is in the root of the mod folder), which if done correctly will cause ModdBuddy to "build" the .modinfo file (a plain text file in the same folder as your mod) to have something looking like this at the end of the file;