1. Relationships & Queries in Databases
Chapter 5
Relationships & Queries in Databases

2. Types of Relationships
One to One
Examples?
Analysis Technique
Consider ThingA and ThingB
Can ThingA be related to more than one ThingB?
Can ThingB be related to more than one ThingA?
If the two answers are NO, then it is a one to one relationship.

3. Types of Relationships
One to Many
Examples?
Analysis Technique
Consider ThingA and ThingB
Can ThingA be related to more than one ThingB?
Can ThingB be related to more than one ThingA?
If the answers are no and yes, or yes and no, then the relationship is one to many.

4. Types of Relationships
Many to Many
Examples?
Analysis Technique
Consider ThingA and ThingB
Can ThingA be related to more than one ThingB?
Can ThingB be related to more than one ThingA?
If the answers are yes and yes, then you have a many to many relationship

5. Leads to Serious Data Redundancy
Hierarchical

6. Hierarchical

7. Network

8. Difficult to manage and implement relationships
Network

9. The most popular structure
Relational

10. Relational Orders Customers Products OID CID PID Quantity CID FName
001
508
199
500,000
002
201 2
003
510 1
Customers
CID
FName
LName
Address
508
Eric
Breimer
...
509
Andrew
Zych
510
Greg
Smith
Products
PID
Description
Cost
199
Viagra
$45.99
200
Tooth Paste
$2.58
201
Hair Gel
$5.99

11. Find the name and hire date of the manager working on the sales manual project

12. Schemas Schema - A description of the database
Subschema – describes a subset of the database and which users have access to this subset

13. Data Definition Language
Language Used to describe Schemas and Subschemas
Describes relationships between different data
Provides a Logical view of the data

14. Data Dictionary Entry
A more detailed description of the data in a database
Specifies data types and ranges
Assists programmers in understanding the data

15. Logical vs. Physical Access Paths
Database Management Systems concentrate on Physical access to the underlying tables
Concurrency control
Query’s
Creating/deleting tables
MIS systems are often software packages that (Logically) interface with a DBMS
monthly reports
charts
automated inquiries