What will be the relation between Employees and Players, given that some players are also Employees?
can you give an example of exactly why there's a N:N with unique constraints for both Emp_id and player_is?

CREATE TABLE employee (employee_id INT PRIMARY KEY, ...);
CREATE TABLE player (player_id INT PRIMARY KEY, ...);
CREATE TABLE junction (employee_id INT NOT NULL,
                       UNIQUE (employee_id),
                       FOREIGN KEY (employee_id) REFERENCES employee (employee_id),
                       player_id INT NOT NULL,
                       UNIQUE (player_id),
                       FOREIGN KEY (player_id) REFERENCES player (player_id));

Unique constraints forbid one employee to be two separate players and backward.
If a player is not an employee than junction table does not contain a row for him, and backward.