AS Level CS (9618) CH8 Database

Database

a structured collection of items of data that can be accessed by different applications programs.

Relational database

a database where the data items are linked by internal pointers.

Table

a group of similar data, in a database, with rows for each instance of an entity and columns for each attribute.

Record (database)

a row in a table in a database.

Field

a column in a table in a database.

Tuple

"one instance of an entity

Entity

"anything that can have data stored about it

Attribute (database)

"an individual data item stored for an entity

Candidate key

"an attribute or smallest set of attributes in a table where no tuple has the same value."

Primary key

"a unique identifier for a table. It is a special case of a candidate key."

Secondary key

"a candidate key that is an alternative to the primary key."

Foreign key

"a set of attributes in one table that refer to the primary key in another table."

Relationship

"situation in which one table in a database has a foreign key that refers to a primary key in another table in the database."

Referential integrity

"property of a database that does not contain any values of a foreign key that are not matched to the corresponding primary key."

Index (database)

"a data structure built from one or more columns in a database table to speed up searching for data."

Entity-relationship (E-R) model or E-R diagram

"a graphical representation of a database and the relationships between the entities."

Normalisation (database)

"the process of organising data to be stored in a database into two or more tables and relationships between the tables

First normal form (1NF)

"the status of a relational database in which entities do not contain repeated groups of attributes."

Second normal form (2NF)

"the status of a relational database in which entities are in 1NF and any non-key attributes depend upon the primary key."

Third normal form (3NF)

"the status of a relational database in which entities are in 2NF and all non-key attributes are independent."

Composite key

"a set of attributes that form a primary key to provide a unique identifier for a table."

Database management system (DBMS)

"systems software for the definition

Data management

"the organisation and maintenance of data in a database to provide the information required."

Data dictionary

"a set of data that contains metadata (data about other data) for a database."

Data modelling

"the analysis and definition of the data structures required in a database and to produce a data model."

Logical schema

"a data model for a specific database that is independent of the DBMS used to build that database."

Access rights (database)

"the permissions given to database users to access

Data definition language (DDL)

"a language used to create

Data manipulation language (DML)

"a language used to add

SQL script

"a list of SQL commands that perform a given task