1. Relational Databases Relational Algebra (2)
Set operators, renaming, notation

2. Relational algebra query (expression) on set of
relations produces relation as a result
College(cName,state,enrollment)
Student(sID,sName,GPA,sizeHS)
Apply(sID,cName,major,decision)
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

3. Relational Algebra (2) Union operator
List of college and student names
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

4. Relational Algebra (2) Difference operator
IDs of students who didn’t apply anywhere
IDs and names of students who didn’t apply anywhere
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

5. Intersection operator
Relational Algebra (2)
Intersection operator
Names that are both a college name and a student name
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

6. Intersection doesn’t add expressive power (1)
Relational Algebra (2)
Intersection doesn’t add expressive power (1)
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

7. Intersection doesn’t add expressive power (2)
Relational Algebra (2)
Intersection doesn’t add expressive power (2)
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

8. Relational Algebra (2) Rename operator 1. 2. 3. College Student Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

9. To unify schemas for set operators
Relational Algebra (2)
Rename operator
To unify schemas for set operators
List of college and student names
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

10. For disambiguation in “self-joins”
Relational Algebra (2)
Rename operator
For disambiguation in “self-joins”
Pairs of colleges in same state
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

11. Assignment statements – Pairs of colleges in same state
Relational Algebra (2)
Alternate notation (1)
Assignment statements – Pairs of colleges in same state
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

12. Expression tree – GPAs of students applying to CS in CA
Relational Algebra (2)
Alternate notation (2)
Expression tree – GPAs of students applying to CS in CA
College
Student
Apply
cName
state
enr
sID
sName
GPA HS
sID
cName
major
dec

13. Relational Algebra (2)
Relational Algebra summary