SQL_employee,department&supervisors

SELECT e.fname, e.lname, e.bdate, e.salary, e.sex, d.dname, concat(f.fname," ", f.lname) FROM employee e, employee f, department d WHERE (e.dno = d.dnumber) AND (e.superssn = f.ssn);

SELECT e.fname, e.lname, e.bdate, e.salary, e.sex, d.dname, concat(f.fname," ", f.lname) AS supervisor FROM employee e LEFT JOIN employee f ON (e.superssn = f.ssn), department d WHERE (e.dno = d.dnumber);

SELECT p.pnumber, p.pname, e.ssn  FROM project p, employee e, works_on  w WHERE e.ssn = w.essn AND p.pnumber = w.pno AND e.ssn=123456789;

SELECT p.pnumber, p.pname, w.essn FROM works_on w RIGHT JOIN project p ON essn=123456789 AND p.pnumber=w.pno;