Relational Algebra

Reading Time: 5 minutes Relational algebra, first described by E.F. Codd while at IBM, is a family of algebra with a well-founded semantics used for modelling the data stored in relational databases, and defining queries on it. To organize the data, first the redundant data and repeating groups of data are removed, which we call normalized. By doing this

Views

Reading Time: 1 minute The relational algebra consists of: a set of eight operators (which ones?) and a relational assignment operation The relational assignment operation allows us to assign a name to the result of a relational expression, for example if we take the product of two relations A and B, then: C ← A X B shows that

Relational Integrity

Reading Time: 2 minutes The relational database schema for The Suppliers and Parts database is shown below: S    (Sno, Sname, Status City) P    (Pno, Pname, Color, Weight, City) SP   (Sno, Pno, Qty) A superkey is an attribute (or set of attributes) that uniquely identifies a tuple in a relation For example the combination Sno,Sname uniquely identifies a tuple in S. A candidate

Relation Model

Reading Time: 1 minute Relation – A table with columns and rows. Attribute – A named column of a relation. Domain – The set of allowable values for one or more attributes. Tuple – A row of a relation. Intension – The structure of a relation (i.e. its attributes), together with a specification of the domains and any other restrictions on possible values. The structure