Summary
IEB IT theory grade 12 LU1 normalization summary
IEB summary of LU1 IT theory from exploring IT by deila kench, covers normalisation
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
Content preview
Relational databases Databases consist of many tables that contain data that is related in some way
- called relational databases
- managed by the DBMS – database management systems
Keys
Primary key
A field in a table that uniquely identifies each record in the table
- no data values in the primary key field are repeated
- shown by underlined word
Super keys
A combination of fields in the tables which uniquely identify each row
- any number of fields that will uniquely identify a record
Candidate keys
Minimal super keys
Primary keys
A minimal candidate key that uniquely identifies a record
composite/compound/concatenated keys
A combination of two or more fields to form a primary key
Normalisation
Database design
- the process of representing a problem in the real world as a set of tables
Normalisation avoids
- repeating groups
- data redundancy
- anomalies (update, insertion, deletion)
- complex queries
Repeating groups and data redundancy
Repeating groups
- a field hat can have multiple values
- when repeating groups are removed, data redundancy is produced
- in databases : all fields should have a single values / not many
Summary
A repeating group ccurs when a field contains more than one value
Repeating groups produce invalid tables since it infringes on the primary key
Inserting multiple values in a cell is not possible
Expanding the primary key produces data redundancy
Anomalies
Update anomaly
Occur when the same data needs to be updated in more than one place
- human error could lead to inconsistencies and if the data in the database is
inconsistent then it is of little value
Deletion anomaly
Occur when a deletion causes unnecessary loss of data
Insertion anomaly
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through EFT, credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying this summary from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller paintingerin1. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy this summary for R50,00. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
81989 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy summaries for 14 years now