Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: What is a Relational Model?
Description: These notes are a brief intro to the basics of relational algebra and are pretty much easier than ever, please don't forget to buy this PDF
Description: These notes are a brief intro to the basics of relational algebra and are pretty much easier than ever, please don't forget to buy this PDF
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
CSC271 Database Systems
Relational Model
Sets and Cross Product
■ Relational model of the data is based on the mathematical foundation
of sets and was proposed by E
...
Codd
...
Dn
● E
...
Person names and City names
■ A relation r is a subset of
D1 x D2 x … x Dn
■ Thus, a relation is a set of tuples (a1, a2, …, an)
where each ai ∈ Di
■ Degree (or arity) of the relation is number of
attributes n involved in the relations
...
g
...
■ Domain is said to be atomic if all its members are
atomic
6
Relation Schema
■ A1, A2, …, An are attributes
■ S = (A1, A2, …, An ) is a relation schema
● Example:
StudentSchema = (name, city, program)
■ r (S) denotes a relation r on the relation schema S
● Example:
student (StudentSchema)
7
Database
■ A database consists of multiple relations
■ Information about an enterprise or a business
function is broken up into parts, with each
relation storing one part of the information
● Student
: basic information about students
● Course:
basic information about courses
● Enrollment
: information about which student
registered in which course
8
Example Database
Student
Enrollment
rn
name
city
program
rn
code
when
01
Junaid
Multan
MSCS
02
101
2014-08-30
02
Sarmad Lahore
BSCS
03
101
2014-09-01
03
Kutab
Lahore
BSCS
04
101
2014-09-01
04
Junaid
Peshawar BSSE
04
123
2015-01-30
02
271
2015-09-01
03
272
2015-09-01
Course
code title
credits lab
04
271
2015-09-02
101
ICT
3
1
03
302
2016-01-30
123
RE
3
0
04
302
2016-01-30
271
DB
4
1
302
HCI
3
0
9
The Banking Schema
■ branch = (branch_name, branch_city, assets)
■ customer = (customer_id, customer_name, customer_street, customer_city)
■ loan = (loan_number, amount)
■ account = (account_number, balance)
■ employee = (employee_id
Title: What is a Relational Model?
Description: These notes are a brief intro to the basics of relational algebra and are pretty much easier than ever, please don't forget to buy this PDF
Description: These notes are a brief intro to the basics of relational algebra and are pretty much easier than ever, please don't forget to buy this PDF