Data Mgmt Lab_Part_6 - 3 THE RELATIONAL MODEL Exercise 3.1...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 3 THE RELATIONAL MODEL Exercise 3.1 Define the following terms: relation schema, relational database schema, domain, attribute, attribute domain, relation instance, relation cardinality , and relation degree . Answer 3.1 A relation schema can be thought of as the basic information describing a table or relation . This includes a set of column names, the data types associated with each column, and the name associated with the entire table. For example, a relation schema for the relation called Students could be expressed using the following representation: Students( sid: string , name: string , login: string , age: integer , gpa: real ) There are five fields or columns, with names and types as shown above. A relational database schema is a collection of relation schemas, describing one or more relations. Domain is synonymous with data type . Attributes can be thought of as columns in a table. Therefore, an attribute domain refers to the data type associated with a column. A relation instance is a set of tuples (also known as rows or records ) that each conform to the schema of the relation. The relation cardinality is the number of tuples in the relation. The relation degree is the number of fields (or columns) in the relation....
View Full Document

Page1 / 3

Data Mgmt Lab_Part_6 - 3 THE RELATIONAL MODEL Exercise 3.1...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online