• For each of the following problems:
  1. Write the relational algebra expression
  2. Write the expression in the form of a query tree

4. Retrieve the SSN of employees who do not work on any project.

EMPLOYEE Sex Salary Super san Dno Fname MinitLname John B Smith 123456789 1965-01-09 731 Fondren, Houston, TX M 30000 333445 Franklin TWong 333445555 1955-12-08 638 Voss, Houston, TX M 40000 888665555 5 Alicia JZelaya 999887777 1968-01-19 3321 Castle, Spring. TXF 25000 9876543214 Jennifer S Wallace 987654321 1941-06-20 291 Berry, Bellaire, TX F 43000 888665555 4 Ramesh K Narayan 666884444 1962-09-15 975 Fire Oak, Humble, TX M 38000 3334455555 Joyce A English 453453453 1972-07-31 5631 Rice, Houston, TX F 25000 333445555 5 AhmadVJabbar 9879879871969-03-29 980 Dallas, Houston, TXM 25000 98765432 4 James EBorg 888665555 1937-11-10 450 Stone, Houston, TX M 55000NULL Bdate Addr DEPARTMENT DEPT LOCATIONS Dnumber Dnumber Mgr start_date 1988-05-22 1995-01-01 1981.06-19 Dlocation Houston Stafford Bellaire Sugarland Houston r ssn Research 33445555 987654321 888665555 Administration 5 WORKS ON PROJECT Essn 23456789 23456789 666884444 340.0 453453453 453453453 33445555 333445555 33445555 10 10.0 333445555 20 10.0 999887777 999887777 987987987 987987987 987654321 987654321 2015.0 888665555 20 NULL Pno Hours 32.5 7.5 Productx ProductY Productz Computerization10Stafford Pnumber Plocation Dnum Bellaire 2 Sugarland5 Houston 5 20.0 20.0 10.0 10.0 20 Houston Newbenefits 30 Stafford DEPENDENT Dependent name Sex Bdate Relationshigp ssn 30 30.0 10 10 35.0 30 30 20.0 F 1986-04-05 Daughter M 1983-10-25 Son 333445555 Alice 333445555 Theodore 333445555 Jo 987654321 Abner 123456789 Michael 23456789 Alice 123456789Elizabeth 10.0 F 1958-05-03 Spouse M 1942-02-28 Spouse M 1988-01-04Son F 1988-12-30 Daughter F 1967-05-05 Spouse 5.0