DBMS Relational Model
We shall represent a relation as a table with columns and rows. Each column of the table has a name, or attribute. Each row is called a tuple.
Relational Model represents how data is stored in Relational Databases. A relational database stores data in the form of relations (tables).
Relational Model was proposed by E.F. Codd to model data in the form of relations or tables.
Domain: a set of atomic values that an attribute can take.
Attribute: name of a column in a particular table (all data is stored in tables). Each attribute Ai must have a domain, dom(Ai).
Relational Schema: The design of one table, containing the name of the table (i.e. the name of the relation), and the names of all the columns, or attributes.
Example: STUDENT( Name, SID, Age, GPA)
Degree of a Relation: the number of attributes in the relation's schema.
Tuple, t, of R( A1, A2, A3,...., An): an ORDERED set of values, < v1, v2, v3,...., vn>, where each vi is a value from dom( Ai).
Relation Instance, r( R): a set of tuples; thus, r( R) = { t1, t2, t3,..., tm}
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