Imagine we have an Employee - Supervision relation like the image below:
Where we can basically retrieve all "Manager - Employee" relations with:
SELECT E.lastName AS "Employee", M.lastName AS "Manager"
FROM Employees E LEFT OUTER JOIN
(Supervisions S INNER JOIN Employees M
ON S.managerID = M.employeeID)
ON E.employeeID = S.employeeID
ORDER BY E.lastName
How could we retrieve a walk from any specific employee to all employees it supervises?
Similarly this relation can be abstracted and applied to anyone saving a graph using 2 tables in any SQL database and trying to walk it.
This question is based on studies from Tom Jewett (where I borrowed images & examples) https://web.csulb.edu/colleges/coe/cecs/dbdesign/dbdesign.php?page=recursive.php