Notes from my Exercise Book
Several of the more common models of databases include:
It is relational databases that are used more commonly than their alternative, flat-file databases. They depend on a sound theoretical basis in relational algebra.
Definitions for relational databases:
"The relational model, which is rooted primarily in the mathematical principles of set theory and predicate logic, supports easy data retrieval, enforces
data integrity (data accuracy and consistency), and provides a database structure independent of the applications accessing the stored data." (Oppel and Sheldon, 2009)
Here are some further definitions that would seem to overlap with the ones provided in my notes above, but those I have already listed are utilised more in the context of SQL whereas the following
are used more in actual relational theory. Definitions from Oppel and Sheldon (2009). SQL: A Beginner's Guide, Third Edition. New York et al: McGraw Hill:
- Relation: "A set of columns and rows collected in a table-like structure that represents a single entity made up of related data."
- Entity: "A person, place, thing, event, or concept about which data is collected, such as a recording artist, a book, or a sales transaction."
- Attribute: "A unit fact that describes or characterises an entity in some way."
- Domain: "[D]efines the type of data that can be stored in a particular attribute [has a much broader meaning than data type - see below]."
- Data type: "A specific kind of constraint (a control used to enforce data integrity) associated with a column." - N.b. restricts the format of data
- Tuple: "A set of data whose values make up an instance of each attribute defined for that relation."
You may find these links useful for pursuing a personal interest in databases and SQL:
2016-2020 Leo Coroneos
Certificate IV in Information Technology
South Regional TAFE, Albany WA Australia