10 Fundamentals Of Databases Flashcards
Data model
An abstract model of what to store and which information about them should be recorded
Entity
An object that has data stored about it
Attributes
Characteristics or other information about entities
Entity identifier
An attribute given to each entity which is unique within that table
Composite key
Multiple attributes which are combined to form the tables entity identifier
Entity description
Describes how information is stored in a table in the database
Give the general set up of an entity description
TableName (column1PrimaryKey , column2, …)
Three types of relationship
One to one
One to many
Many to many
Entity relationship diagrams
Graphically represents the relationships between tables in a database
Primary key
An attribute that provides a unique identifier for every entity in a database table
Foreign key
A primary key that is an attribute in another table
Why are databases normalised
Allows them to be efficient without compromising the integrity of the data
Allows faster sorting and seaching
First normal form
No repeating attributes
Atomic - no single column contains more that one value
Second normal form
Satisfies the first normal form
Partial key dependencies are removed (no composite keys)
Third normal form
Satisfies the second normal form
No non key dependencies (attributes should only depend on the primary key)
