SQL QUERY - DATABASE APPLICATION

SELECT E.* S.lname FROM employee E JOIN employee S ON (E.superssn = S.ssn);

No Supervisor:
SELECT E.* S.lname FROM employee E LEFT JOIN employee S ON (E.superssn = S.ssn);

Combining fname AND lname:
SELECT E.* S.lname CONCAT(S.fname," "S.lname) AS supervisorname FROM employee E LEFT JOIN employee S ON (E.superssn = S.ssn);

Relating department NUMBER TO dno:
SELECT E.* S.lname, D.dname CONCAT(S.fname," "S.lname) AS supervisorname FROM employee E LEFT JOIN employee S ON (E.superssn = S.ssn), department D WHERE (E.dno=D.dnumber);