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W7 - Database Management System - Coggle Diagram
W7 - Database Management System
Database
Are organized + have a structure, every data we store in them fits in this structure
Simple database: Flat file database
stores data in columns of fields and rows of records
fields as columns and records as rows
FIELDS can have 6 different types
text
number
date
time
graphic
caculated
Relational database
allows users to identify + access data in relation to other pieces of data in the database based on business rules or associations
Advantages over flat file storage and non-relational databases
Data integrity
Reduction of data publication
Database System
Enterprise database system
Commercial Database system
Data warehouse
Another layer sits between the database and the user
takes the data from all these databases + creates a single source of truth , layer optimized for and dedicated to analytics
Data Marts
Subsets of Data Warehouse, contain repositories on a spevific business unit/department within an organisation
More focused on a single area
Support tactical decisions & decisios imapcting a business unit as opposed to the whole organisation
provides summarized and analyzed data as opposed to raw unprocessed data
Relational Database Design
ERD
Comprised of 3 main factors
Entities
Attributes
Relationships
Main aspect: cardinality
further define the relationship in a numerical context between minimum and maximum
Keys
Primary Keys
an attribute/field that uniquely identifies every record in a certain table
1 primary key/entity
characteristic: unique, never-changing, never-null
Foreign Keys
an attribute in one entity that links to te PK of another entity => enable relationship between those entities
can be multiple FK/entity
Composite primary keys
are used when 1/2/ more attributes are necessary to uniquely identify every record in a table
Bridge Table