ISM 671

raw facts or facts that haven't been processed yet to reveal their meaning to the end user.

the result of processing raw data to reveal its meaning

the process of data collection, storage and retrieval.

houses a collection of related data; it has 2 types of data: end-user data & metadata

data about data; it defines data characteristics and the relationships

serves as the intermediary between the user and the database. it manages the DBS structure and controls access to the data stored.

• Data is organized into one or more two dimensional tables in which each table contains the data RELATING to a specific type of entity.
• (relation = table)

a row

translates user requests into commands that locate and retrieve data (using SQL engine - structured query language).

a graphical representation of  relational database's entities, their attributes and relationship among the entities.

all entities and relationships in a diagram

by software, giving a command to create a table, etc.

...when different people have a different views of the database

• Functional dependency: the value of one attribute determines the value of one or more other attributes
• ex: student ID (determinant) → student last name (dependent)

FULL dependence: a collection of attributes (composite key) determines the value of the other attributes

ex: student first name, last, middle initial

entity & referential integrity

• Entity (PK): must be unique and can't be null
• Referential (FK): it may be null as long as it is not a part of the table's PK. If there is a value in another table, it must match the value in its native table (a table to which it is related or it comes from).

• - entity
• - attributes
• - relationships

• shows the frequency of entity occurences 
• (1,1) min of 1 max of 1