in the base case of the inductive definition of the operations of the relational algebra there is also the so called "constant relation" (as for example found in the definition here https://www2.cs.sfu.ca/CourseCentral/354/zaiane/material/notes/Chapter3/node9.html). However, until now I have not understood the following points:
- what is it?
- what is it good for?
- what does it look like?
- can one use it to create "customized" databases (i.e. that I can define them completely manually by inserting the elements that I want)?
Thanks for you help!