Summary
Summary Unit 2 Creating system to manage information Keywords
- Institution
- PEARSON (PEARSON)
it for unit 2 and its about the definitions of the keywords.
[Show more]
Seller
Follow
Content preview
Name: Sabiha ChoudhuryBMC171817858
Unit 2 Creating systems to manage information
Classwork Homework
Primary Key
Primary keys (columns) in a table are a minimal set of attributes that uniquely identify each
tuple (row) in the table. The database designer can select any of the candidates as the
primary key on a table if it contains one primary key.
Table rows should all have unique values for the primary key.
The primary key of a table is usually one of the fields, which can either be a number
or another data type.
One of the main attributes of a primary key is that it must contain a unique value
for each row of data and null values are not permitted.
Foreign Key
In a relational database table, a foreign key is a column or field that links records in two
different tables. It does this by referencing the primary key of one table and accessing it
through another table. For foreign keys to function, two tables need to be given a
relationship.
Candidate Key
Candidate keys are the fields that contribute most to uniquely identifying a tuple.
Candidates keys refer to the fields from which the primary key can be selected. In SQL,
candidate keys may contain multiple attributes. The main purpose of the candidate is to
offer multiple options to the database designers so that suitable primary key can be
selected.
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 credit card 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 these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller sabihachoudary. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £8.89. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
70055 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now