Databases Flashcards
Entity
a category of objects, person or thing of interest of which data needs to be recorded
Field
give category headings for each item of data in a database (e.g. Time, Date, Right Ascension, etc.) - also known as attributes
Record
a collection of data for one object/person/thing - shown as a single row in a table
Table
made up of records and fields and is a collection of related data
Primary key
field(s) in a database table that act as a unique identifier for each record
Composite primary key
includes two or more attributes to uniquely define a record
Foreign key
an attribute that creates a connection between two tables
Relational Database Management System (RDBMS)
provides an interface between users and applications and the database
Flat file
type of database that stores data in a plain text format
Normalisation
process used to create the best possible design for a database
First normal form
contains no repeating attributes/group of attributes
Second normal form
a table is in 2NF if it’s in 1NF AND contains no partial-key dependencies
Third normal form
a table is in 3NF if it’s in 2NF AND contains no non-key dependencies
Partial key dependency
occurs when one primary key determines some other attribute(s)
Referential integrity
refers to the accuracy and consistency of data within a relationship
Client-server database
when a database resides on a server and client applications are written to access the database
Record locking
prevents simultaneous access to objects in a database to prevent updates being lost or inconsistencies in the data from occuring
Serialisation
technique used to ensure that transactions don’t overlap in time
Timestamp ordering
each object in database has a read timestamp and write timestamp - updated whenever an object is read or written
Commitment ordering
another serialisation technique that ensures no transactions are lost if two clients are trying to update a record simultaneously
