What is the difference between covering and overlapping constraints use in DBMS?
In reference with below Employee Entity Relational Model




Overlap Constraints : Can "Karthik" (employee) be an Hourly_Emps as well as a Contract_Emps entity? (Allowed/Disallowed) - In this scenario the hourly employee karthik cannot be a contract employee - Disallowed - This explains the Overlap constraints.
Covering Constraints : Is every hourly employee and every contract employee an employee of this organization? Answer: Yes, all the contract/hourly employees belong to the master employees entity - This explains the Covering constraints.