1. Chapter 3 Supplemental Slides
Relational Division Demonstration
Welcome to the relational division demonstration:
- Supplemental slides for chapters 3 and 9
- More of an interactive demonstration than an animation
- See the derivation of rows in the result of a relational division operation
- Demonstration should help you understand relational division, a more complex
operator than the join operator
- Division problems are not common
- Important when occurring
- Provide expert query formulation knowledge
- This demonstration complements the static presentation in the lecture notes and textbook.
- Play it yourself at your own pace

2. Relational Division Animation
Part
PartNo P1 P2 P3
SuppPart
SuppNo
PartNo S2 P3 S3 P1 S1 P2
Relational division:
- Specialized operator for subset matching
- Find suppliers who supply an interesting subset of parts
- Find professors who teach an interesting subset of courses
- Find students who have taken an interesting subset of courses
Table structure:
- Two column table divided by a one column table
- Can be extended for tables with more columns but not necessary for this course
Table structure
- SuppPart table: combinations of suppliers and parts; M-N relationship between
Supp and Part tables
- Part table: contains all parts; only show the PartNo column
Problem:
- List SuppNo values that are associated with all (every) PartNo
- Difficult to see: S2 is associated with P1, P2, and P3
- Rearrange values of SuppPart table to see more clearly the associations between
SuppNo and PartNo values

3. Relational Division Animation
SuppPart
SuppNo
PartNo S1 P1 P3 S2 P2 S3
Part
PartNo P1 P2 P3
Sort the SuppPart table by SuppNo
- Easier to see that only S2 should be in the result
Let’s see operation of the division operator for each SuppNo value in the SuppPart table
Sort SuppPart by SuppNo

4. Relational Division Animation
SuppPart
SuppNo
PartNo S1 P1 P3 S2 P2 S3
Part
PartNo P1 P2 P3
Result table contains a single column: SuppNo
Processing of first SuppNo value:
- SuppNo S1 is associated with PartNo P1 and P2
- SuppNo S1 is not in the result
SuppPart DIVIDEBY Part
SuppNo
S1 {P1, P3} does not contain {P1, P2, P3}.

5. Relational Division Animation
SuppPart
SuppNo
PartNo S1 P1 P3 S2 P2 S3
Part
PartNo P1 P2 P3
Processing of second SuppNo value:
- SuppNo S2 is associated with PartNo P1, P2, and P3
- SuppNo S2 is in the result
SuppPart DIVIDEBY Part
SuppNo S2
S2 {P1, P2, P3} contains {P1, P2, P3}.

6. Relational Division Animation
SuppPart
SuppNo
PartNo S1 P1 P3 S2 P2 S3
Part
PartNo P1 P2 P3
Processing of last SuppNo value:
- SuppNo S3 is associated with PartNo P1
- SuppNo S3 is not in the result
SuppPart DIVIDEBY Part
SuppNo S2
S3 {P1} does not contain {P1, P2, P3}.