Databases

An abstract model of which things to store and what information about them should be recorded

A thing about which data is to be stored

Characteristics or other information about entities

Tables used to store multiple entities

An attribute given to each entity that is unique within the table

The name of the table is shown outside of brackets (which contain each of the attributes)

The tables in a database are connected by common attributes

Used to graphically represent the relationships between tables in a database

An attribute that provides a unique identifier for every entity in the database table

The attribute that is the primary key in the other, connected table

Combining multiple attributes that act as a primary key

A new linking table must be created

The process of making a database efficiency without compromising the integrity of the data

• Reduced redundancies • Faster searching, sorting and querying of data • Easier maintenance • Improves data integrity

No repeating attributes (data must be atomic)

• Be in 1NF • No partial key dependencies

When a non-key attribute doesn’t depend on the entire composite primary key

• Be in 2NF • Have no non-key dependencies

When a non-key attribute is dependent on other no-key attributes instead of the primary key

An easy to learn, declarative language used with databases

• Used for retrieving data from a database table • SELECT <attribute> FROM <table> WHERE <condition></condition></attribute>

• Used for modifying the attributes of an existing entity • UPDATE <table> SET <attribute> = <value> WHERE <attribute> = <value></value></attribute></value></attribute>

• Used for removing entities from a database • DELETE FROM <table> WHERE <condition></condition>

• Used to add new records to an existing table • INSERT INTO <table> (<column1>, <column2>, …) VALUES (<value1>, <value2>, …)</value2></value1></column2></column1> • INSERT INTO <table> VALUES (<value1>, <value2>, …)</value2></value1>