CS5200 – Database Management Systems Fall 2017 Derbinsky

Exam 2 Review

Lecture 11

October 31, 2017

Exam 2 Review

1

CS5200 – Database Management Systems Fall 2017 Derbinsky

Format

• 3 problems, with multiple sub-parts

• No notes, calculators, books, computers, phones, etc. may be used

October 31, 2017

Exam 2 Review

4

CS5200 – Database Management Systems Fall 2017 Derbinsky

ContentConceptual/Logical database design…

– ER Diagrams–Mapping ER Diagrams to Relations– Normalization

October 31, 2017

Exam 2 Review

5

CS5200 – Database Management Systems Fall 2017 Derbinsky

ER Diagrams & Mapping• Conceptual design: goals, approaches• All the notation we covered– Entities: weak/strong– Attributes: composite, multi-valued, derived,

keys– Relationships: cardinality, structural, attributes– Specialization/Generalization– When to use!

• Mapping to tables– Multiple methods for specialization/generalization

October 31, 2017

Exam 2 Review

6

CS5200 – Database Management Systems Fall 2017 Derbinsky

Exercise• Describe in words the

following ERD– How can you identify

an instance of E?

• Map E to relation(s)– What are the primary

key(s)?– What happens to

other key(s)?

October 31, 2017

Exam 2 Review

7

mv E

a1

id2

a4a3

id1

d

CS5200 – Database Management Systems Fall 2017 Derbinsky

Answer• All E’s have an a1, an id1, an id2 composed

of a3 and a4, and some number of mv’s. By combining these you can determine the E’s d.

• An E can be uniquely identified by either its id1, or the combination of a3 and a4.

October 31, 2017

Exam 2 Review

8

id1 a1 a3 a4E

id1 mv

MV

CS5200 – Database Management Systems Fall 2017 Derbinsky

ExerciseProduce an ERD & corresponding relational schema

• An S has an sa and can be uniquely identified by its sid

• Each S must R2 with a single O2, whereas each O2 may R2 with any number of S’s. When an S R2’s an O2, it is important to note the corresponding ra2

• An O2 has an x and can be uniquely identified by its o2_id, which is comprised of p1 and p2

• A W is identified by its corresponding S, in combination with its own wid, consisting of a wa and wb

• Each W can R1 with any number of O1’s, and likewise each O1 can R1with any number of W’s. Each R1 interaction has a corresponding ra1

• An O1 is uniquely identified by its o1_id and also has an x

October 31, 2017

Exam 2 Review

9

CS5200 – Database Management Systems Fall 2017 Derbinsky

Answer (1)

October 31, 2017

Exam 2 Review

10

S

sid sa

O2

R2 ra2

o2_id

x p1 p2

ID W

R1

O1o1_id

x

ra1

sidwb

wa

N

1

N1

N

M

CS5200 – Database Management Systems Fall 2017 Derbinsky

Answer (2)

October 31, 2017

Exam 2 Review

11

sid sa p1 p2 ra2S

p1 p2 xO2

sid wa wbW

o1_sid sid wa wb ra1R1

o1_sid xO1

CS5200 – Database Management Systems Fall 2017 Derbinsky

1

Exercise

October 31, 2017

Exam 2 Review

12

P

PID

C1 C2

Ud

PA

A1 A2

R

E

EID EA

N

MapthisERDtorelationsintwo differentways.Prosandconsofeach?

CS5200 – Database Management Systems Fall 2017 Derbinsky

Answer

October 31, 2017

Exam 2 Review

13

pid paP

pid a1C1

pid a2 eidC2

eid eaE

eid eaE

pid pa a1C1

pid pa a2 eidC2

CS5200 – Database Management Systems Fall 2017 Derbinsky

Normalization• What are the goals of normalization?– Spurious tuples? Additive decomposition?– Modification anomalies? Examples!

• Functional dependencies– Definition, relationship to keys– Trivial, transitive, full

• Normal forms– What do 1NF/2NF/3NF require?– Decomposition algorithm

October 31, 2017

Exam 2 Review

14

CS5200 – Database Management Systems Fall 2017 Derbinsky

Exercise

October 31, 2017

Exam 2 Review

15

Non-Trivial FDs Key(s)

S T U V W

S ! T

TU ! WVW ! S

UV SUVWUV T

CS5200 – Database Management Systems Fall 2017 Derbinsky

ExerciseWhich NF? Why? Decompose to 3NF.

October 31, 2017

Exam 2 Review

16

X Y Z

M N O P

Foo

Bar

CS5200 – Database Management Systems Fall 2017 Derbinsky

Answer• Foo is in 2NF– 1NF (single PK attr)– Y is tFD on PK– Post: single PK/np

• Bar is in 1NF– P is not fFD on PK– Post:

• Bar: N fFD on PK, single PK/np

• O: single PK/np

October 31, 2017

Exam 2 Review

17

X ZFoo

Z YZ

M N OBar

O PO