1. Chapter 3 Supplemental Slides
Natural Join Demonstration
Welcome to the natural join demonstration:
- See the derivation of rows in the result of a natural join operation
- Complements the static presentation in the lecture notes and textbook
- Can use with Chapters 3 or 4
- Understanding the join operator is crucial for developing query formulation skills
- Repeat this exercise yourself (own small tables ) until the join operator
becomes second nature
- Play it yourself at your own pace using Powerpoint notes

2. Natural Join Animation
Offering
OfferNo
FacSSN
1111
2222
3333
Faculty
FacSSN
FacName
JOE
SUE
SARA
To begin the animation, let's use small input tables:
- Small version of the Offering and Faculty tables used in textbook chapter 4
- Use small versions because of screen limitations and focus attention on essential ideas
- Same ideas apply to tables with more rows and columns
- Using small tables can help you to understand the natural join operation
- Useful for difficult problems especially in textbook Chapter 9
Join condition: Faculty.FacSSN = Offering.FacSSN (highlight columns)
- Natural join requires same unqualified names and equality as comparison operator
Matching rows:
- First Faculty row matches with rows 1 and 3 of Offering (point)
- Second Faculty row matches with row 2 of Offering (point)
- Third Faculty row does not match any Offering rows
- Natural join: discard one of the join columns (one column is duplicate)
- Column discarded does not matter here

3. Natural Join Animation
Offering
OfferNo
FacSSN
1111
2222
3333
Faculty
FacSSN
FacName
JOE
SUE
SARA
First Offering row combines with the first Faculty row
Notice that the OfferNo column comes from the Offering table
The FacSSN and FacName columns come from the Faculty table.
Faculty Natural Join Offering
OfferNo
FacSSN
FacName
1111
JOE

4. Natural Join Animation
Offering
OfferNo
FacSSN
1111
2222
3333
Faculty
FacSSN
FacName
JOE
SUE
SARA
Second Offering row combines with the second Faculty row
Faculty Natural Join Offering
OfferNo
FacSSN
FacName
1111
JOE
2222
SUE

5. Natural Join Animation
Offering
OfferNo
FacSSN
1111
2222
3333
Faculty
FacSSN
FacName
JOE
SUE
SARA
Third Offering row combines with the first Faculty row
Third Faculty row does not combine with any Offering rows: faculty not teaching.
Repeat this exercise yourself using your own small tables
Faculty Natural Join Offering
OfferNo
FacSSN
FacName
1111
JOE
2222
SUE
3333
JOE