What is the difference between covering and overlapping constraints use in DBMS? 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.