1.3.2 Databases - Atharwa Flashcards
What is an Entity?
An item, object or thing a database is about
What is a flat-file database?
A database where data is all stored on one large table
What is a relational database?
Data stored in separate tables linked with foreign keys
What is a Primary key?
A field which can be used to uniquely identify a record
Name ways of collecting data
Webforms, Barcodes, QR codes, Written forms with optical character recognition, Magnetic ink/ stripes
What are the requirements of 1NF?
Must have a primary key, data must be atomic, no repeating attributes, each field must a unique.
What are the requirements of 2NF?
Must be in 1NF, no partial dependencies.
What are the requirements of 3NF?
Must be in 2NF, no transitive dependencies.
What is a partial dependency?
When a field only depends on a part of a composite key, not all of it.
What is a transitive dependency?
When a field depends on another field that isn’t a primary/composite key
What is a transaction?
A change made to a database.
What is meant by Atomicity?
A transaction must be fully completed for it to be recorded.
What is meant by Consistency?
Any changes made must not break the database, keeping it consistent with how it was before.
What is meant by Isolation?
A transaction must be kept isolated so it doesn’t interfere with other transactions.
What is meant by Durability?
A transaction must remain in the database once saved
