Talk:Relational Database Design

Table ripped from http://en.wikipedia.org/wiki/Relational_database#Terminology

More: (not from wiki) all from

- Database Systems: Design, Implementation and Management 8th edition page 32 Peter Rob, Carlos Coronel 2009 Course Technology, Cengage Learning

(first two are not unique to relational databases, apparently)

entity: "An entity is anything (a person, a place, a thing, or an event) about which data are to be collected and stored. An entity represents a particular type of object in the real world. Because an entity represents a particular type of object, entities are "distinguishable" that is, each entity occurrence is unique and distinct. For example, a CUSTOMER entity would have many distinguishable customer occurrences, such as John Smith, Pedro Dinamita, Tom Strickland, etc."

relationship: "A relationship describes an association among entities. For example, a relationship exists between customers and agents that can be described as follows: an agent can serve many customers, and each customer may be served by one agent."

page 111 of the same book.

cardinality: "Cardinality expresses the minimum and maximum number of entity occurrences associated with one occurrence of the related entity."

// That sentence meant jack to me. An example would be better:

STUDENT has a relationship with CLASS.

For each CLASS, how many students can there be?

Minimum 1. Can't be 0, or there would not be a class.

Maximum 30 (an arbitrary number).

Or something like that. Keep in mind I have no idea what I'm talking about.

Primary key (talk) 10:52, 12 June 2009 (UTC)

= Commercial-Grade = The usual standard textbook on this subject, Database Management Systems by Ramakrishnan and Gehrke, is difficult to understand. This presents an opportunity for the Wikibook to become the new standard text for an introductory undergraduate course, but this means it will need to be a bit more rigorous and complete. I'd like to work in this direction, but I could use some help. Durette (discuss • contribs) 03:09, 11 March 2015 (UTC)