Tallahassee, Florida, 2015

COP4710

Database Systems

Midterm Review

Fall 2015

Midterm Exam

• Time: Wednesday 10/15/2014 3:35pm --- 4:50am– Plan your time well

• Venue: HWC 2400, in-class exam

• Closed book, closed note, but you can bring a one-page cheat sheet (A4, double side)– Plan your strategy well

• No calculators or other electronic devices– Laptops, ipads, smart phones, etc. are prohibited

• Any form of cheating on the examination will result in a zero grade, and will be reported to the university

2

Midterm Exam

• 15% of your final score• Format

1. Short-answer questions: testing for basic concepts• Make your answers clear and succinct

• Example 1: What is the difference between Cartesian product and natural join?

• Example 2: Given a relation R in 3NF, is R in BCNF? Why?

2. Relational algebra

3. Relational design

4. SQL

3

Midterm Exam

• What will be covered?– From “introduction” to “SQL-basics” (the end of

today’s class)

– Materials in both the slides and the textbook

• How to do well in the midterm exam?– Review the materials carefully and make sure you

understand them

– Reexamine the homework and make sure you can work out the solutions independently

– Discuss with your peer students

– Discuss with the TA and me

– Relax 4

DB: What and Why?

• Besides file systems and OS, why bother yet another so-called DBMS?

• Schemas & Data• DDL & DML

5

ER Model: Nothing but Drawing

• Entities – Attributes

• Relationships– One-one, one-many, many-many– Roles

• Subclasses• Constraints

– Keys, referential integrity, etc.

• Weak Entity Set: Why & How?

6

Relational Model: A Step Further

• Relation Schema: revisited

• Primary key, Foreign key, Unique, NULL, Default

• Translating ER to Relations– Entities

– Relationships (many-many, many-one, one-one)

– Weak entity set

– Subclass

7

Relational Algebra: Let’s Do Math

• Operators and operands– Set-based operators

– Other basic operators

– Derived operators

• Cartesian product, theta-join, equi-join, natural join

• Relational algebra expressions and expression trees– How to answer queries using relational algebra?

8

Relational Design: Design it right

• Motivation• Functional dependencies & keys

– Armstrong axioms– Closures

• Normal forms and decomposition algorithms– BCNF

• Lossless or lossy?

– 3NF• Functional-dependency preserving or not?

• Don’t overdo it

9

SQL: Let’s Get Hands Dirty

• What is SQL?• Why SQL?

– DDL & DML in SQL

• Select-From-Where– String pattern matching– 3-value logic– How to answer queries using SQL?

10

Break a Leg!