CSIS 350 – Lecture 2
Last time
- We saw that we frequently use systems that include a database as a major component:
WebOpus, on-line retailers, cell phone directory, ATMs,…
- Looked at definitions of database
oSystem for storing data so that information can be derived from it.
oData = recorded facts and figures
oInformation = knowledge derived from data
- Looked at what a DBMS is
oSystem that creates, processes, and administers the database.
oCollection of components that supports creation, use, and maintenance of
databases.
- Looked at some data models used by DBMSs: hierarchical, network, relational
oThis class focuses on the relational model
Relational Model
Invented in 1969 by E.F. Codd at IBM
Not commercially developed until late 1970s
Most DBs today use relational model
Data is stored in relations, which appear to be tables
Each record in a relation is uniquely identified
Unlike hierarchical and network models, where the data is stored does not matter – there
are no physical links in the database.
Types of databases
Discuss types of databases: processing and analysis
- transaction processing (online transaction processing - OLTP)
ogrocery store inventory, bank account
odata must be updated in "real-time"
- analysis/decision support (OLAP – OL analytic processing)
oHuge databases and complex queries
History of all transactions from all grocery stores over last 10 years
What % of our customers who buy crackers also buy cheese?
oDon't need to update often, because it doesn't materially affect query results.
- data mining
oAnother type of analysis
oMuch more open-ended – "knowledge discovery"
Are there any interesting combinations of items that are bought by our
customers?
