Flashcards in Databases Deck (20):
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Define the word database
A database is a structured collection of data
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What's a database management system?
A database management system is a software system that enables the management of a database. E.g access, SQL, ORACLE
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What's a data model
A method of describing the data, it's stucture.
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What's an entity
An entity is an object/person/event about which data is recorded
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What's a relationship?
A relationship is an association or link between two entities
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What are names for a row?
A record or a tuple
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What are other names for a column
Field and attribute
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What is entity occurrence
The details of one instance of the entity
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What's a primary key
An unique attribute which uniquely identify a tuple
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Relational database is?
A collection of tables
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What's composite key
A combination of attributes that uniquely identify a tuple
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What's a foreign key?
An attribute in one table that is a primary key in another table
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What is meant by normalised entities
A set of entities that contain no useless/redundant data
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What's normalisation
A technique used to produce a set of normalised entities
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What's 1NF
Table have primary key and there's no repeating groups of attributes (atomic values)
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What's 2NF
Must be 1NF and contain no partial key dependencies - where the values of the attributes are all independent on the primary key
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What's 3NF
Table is in third normal from if it is in 2NF and where no attributes are predictable because of any other attributes
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What does SQL stands for?
Structured query language
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Why is 3NF important?
It improves consistency
No unnecessarily repeated data
Eliminate update/insertion/deletion anomalies
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