DESelect can provide you with a Demo Data package, which contains a bunch of data extensions with demo data, which you can use for demoing or training purposes.
An overview of common queries that could be built with the Demo Data Package can be found here. These scenarios are great for demoing different functionalities of DESelect or testing training participants' knowledge.
Demo Data Structure
An overview of the structure of the data extensions in the Demo Data Package can be found here.
How To Get The Demo Data Package
This data is installed by default when DESelect is installed. You can find it under Data Extensions (eg. in Email Studio) in a folder called DESelect Demo Data.