Another Question I came across few days ago. This question tests your understanding of SQL Hierarchical Queries and SELF JOIN. Given the following Employees table:

 

Job Interview Question - Hierarchical Queries

 

Note that this table has a certain hierarchy of employees and managers, such that a certain employee may also be a manager. For example, employee number 7 (Merlin Evans) is also the manager of Elroy Wilson, Charles Thomas, and Rudolph Roberts.

 
First Task – Create a query to display the name of all employees, and the name of their manager.
 

Job Interview Question - Hierarchical Queries

 

Second Task – Create a query to display the hierarchical relationship between a certain employee and his direct and indirect managers.
For example, for employee number 7, the query will display the following result (Merlin reports to Jose, and Jose reports to Alvin):

 

Job Interview Question - Hierarchical Queries

 

For employee number 10, the query will display the following result (Rudolph reports to Merlin, Merlin reports to Jose, and Jose reports to Alvin):

 

Job Interview Question - Hierarchical Queries