Sources extension for Universal Content Puller. The sources in this extension are XX because they are the kind of source you may not want to let just anyone loose with, hence a separate package so they don't have to be installed with less sensitive sources.
You can see a demonstration at Example - Site Database.
These are also a starting points for developing custom data sources with more complex database queries. Copy and rename the Site Database or Any Database source for your custom source and then code your more complex query into it.