Explanation:
Employee Table will all constraints can be created by the following command.

 CREATE TABLE employee ( 
 employee_id NUMBER, 
 emp_lname VARCHAR2(25), 
 emp_fname VARCHAR2(25), 
 dept_id NUMBER, 
 job_id NUMBER, 
 mgr_id NUMBER, 
 salary NUMBER(9,2), 
 hire_date DATE, 
 CONSTRAINT employee_id_pk PRIMARY KEY(employee_id), 
 CONSTRAINT dept_id_fk FOREIGN KEY(dept_id) REFERENCES department(dept_id), 
 CONSTRAINT job_id_fk FOREIGN KEY(job_id) REFERENCES job(job_id), 
 CONSTRAINT mgr_id_fk FOREIGN KEY(mgr_id) REFERENCES employee(emp_id));  

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