2.5 Databases and distributed systems Flashcards
What is normalisation?
A staged process which removes repeated groups of data and inconsistencies.
What is the difference between a primary and a foreign key?
A primary key is unique and used to identify a record whereas a foreign key is a field of one table which is also the primary key of another table (links tables together).
What is the difference between a flat file and a relational database?
A flat file database is one table which holds all data however a relational database is a large, organised collection of data items stored in tables which link to other tables and can be accessed in many ways throughout the program.
What are 5 advantages of relational databases?
Data Consistency
No Data Redundancy
Data Integrity
Data Independence
Better Security
What is Data Consistency?
Data Consistency is the relationship between the input data, the processed data and the output data as well as other related data.
Changes made to data is controlled so that the specific data value is consistent throughout the whole database.
What is Data Redundancy?
Occurs when duplicate data is available in multiple tables. This wastes storage and could potentially compromise data consistency.
What is Data Integrity?
It is the correctness of data e.g. the extent to which it truthfully represents the original information.
What is Data Independence?
Refers to the separation of information from the applications and programs that use it. New systems/programs can still develop/use this data without having to change it or modify the source code.
What are three examples of security in a relational database?
Hierarchy of passwords - Limits users to certain parts of the program.
Access rights to parts of the program - Only certain users can access and change data.
Data is stored separately from the program.
How can products in a supermarket have a One to One entity relationship to a barcode?
Every product in the supermarket will have a unique barcode number.
How can a member of a library have a One to Many entity relationship with the books?
A member of a library can take home multiple books therefore, all the books will have the same, temporary owner.
How can teachers have a Many to Many entity relationship with pupils in a school?
Teachers can teach many pupils across the day however, the pupil will also be taught by many teachers throughout their day.
How can many-to-many relationships be improved?
They can be replaced by a one-many-one relationship.
What is Big Data?
Data which involves very large, complex datasets therefore traditional databases are unable to process them under acceptable time frames.
What are four examples of Big Data?
Transactional data from ecommerce.
Machine data from GPS.
RFID Readers.
Social Media interactions.