Primary key - It is the first key which is used to identify one and only one instance of an entity uniquely
Candidate key - Key that consists of two or more attributes that uniquely identify any record on a table
Foreign key - a primary key that i s used to connect two tables

First normal form
    * contains only atomic values
        * atomic value is a value that cannot be divided
    * It states that an attribute of a table cannot hold multiple values. It must hold only single-valued attributes.

Second normal form
    * It is in first normal form
    * All non-key attributes are fully functional dependent on the primary key
        * Non-key attributes are the attributes or fuelds of a table, other than candidate key attributes/fields on a table.
    * Composite key - a key of two or more attributes that uniquely identifies the row. (customer id and store id)
    * Non-key attribute is purchase location

Third normal form
    * it is in second normal form
    * there is no transitive functional dependency
        * a is functionally dependent on b, and b is functionally dependent on c. in this case, c is transitively dependent on a via b
    * now all non-key attributes are fully functional dependent only on the primary key. in [table_book], both [gendre id] and [price] are only dependent on [book id]. in table [table_genre], [genre type] is only dependent on [genre id]

================================================================================

Hva er "Big data"
Frank Danielsen

================================================================================

Hva er?
Hva kan det brukes til?
Hvordan brukes det i dag?

+------------------------------------------------------------------------------+

Store og komplekse dataset, som ikke er lett for mennesker å gå gjennom.

Four V's
    Volume - The scale of the datas
    Variety -
    Velocity -
    Veracity - Uncertainty if data