1. Student(sid, name, addr, age, GPA) Class(dept, cnum, sec, unit, title, instructor) Enroll(sid, dept, cnum, sec) siddeptcnumsec 301CS11201 301CS14301 303EE14301 303CS11201 401CS11201 sidnameaddrageGPA 301John183 Westwood192.1 303Elaine301 Wilshire173.9 401James183 Westwood173.5 208Esther421 Wilshire203.1 deptcnumsecunittitleinstructor CS1120103ModelingDick Muntz CS1430104DB SystemsCarlo Zaniolo EE1430103SignalDick Muntz ME1830205MechanicsSusan Tracey

2. Division R: A table when all students take all CS courses R – Enroll: siddeptcnumsec 301CS11201 301CS14301 303CS11201 303CS14301 401CS11201 401CS14301 208CS11201 208CS14301 siddeptcnumsec 303CS14301 401CS14301 208CS11201 208CS14301

3. Division π sid (R − Enroll): π sid (Student): π sid (Student) - π sid (R − Enroll): sid 303 401 208 sid 301 303 401 208 sid 301

4. Relational Algebra: Things to Remember Data manipulation language (query language) – Relation  algebra  Relation Relational algebra: set semantics, SQL: bag semantics Operators: σ, ×, , ρ, , −, , ⁄ General suggestion: If difficult to write, consider its complement