ISYS111 Lecture Notes - Lecture 10: Online Analytical Processing, Strategic Business Unit, Data Mart
17 Jun 2018
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• How structured query language (SQL) works:
o SQL allows people to do complicated searches using simple statements
or key words
o Query uses terms such as SELECT, FROM and WHERE to create
questions used to search the database
Data warehouses and data marts:
• Difference between data warehouses and data marts:
o Data warehouse:
• Contains historical data
• Data are organised according to subject for easy access
• Organisations often place data from older computer systems (called
"legacy systems") into a data warehouse for future access
o Data marts:
• Smaller version of data warehouse
• Contains information needed by individual departments or strategic
business unit
• Easier to implement and maintain a data mart as it is smaller and
data can be accessed faster
• Characteristics of a data warehouse:
o Organised by business dimension or subject (customer, vendor, product)
so that data is easily searchable
o Uses online analytical processing, meaning the database analyses the data
that have been accumulated by end users, rather than the current
transactional data
o Integrated: data collected from multiple systems are then organised
around subjects
o Time variant: time is used as a variable in the database, because data
warehouses collect historical data, not just current data
o Non-volatile: no one can change or update the data
o Multidimensional: data warehouse stores data in more than two
dimensions (relational database stores data in a two-dimensional table)
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