Transcription of Databases Model the Real World The Entity- “Data Model ...
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Databases Model the Real World The Entity- “Data Model ...
The Entity- Relationship ModelR &G - Chapter 2A relationship, I think, is like ashark, you know? It has toconstantly move forward or itdies. And I think what we got onour hands is a dead Allen (from Annie Hall, 1979) Databases Model the real World data Model allows us to translate real worldthings into structures computers can store Many models: Relational, E-R, O-O, Network,Hierarchical, etc. Relational Rows & Columns Keys & Foreign Keys to link in database Design Requirements Analysis user needs; what must database do? Conceptual Design high level descr (often done w/ER Model ) Logical Design translate ER into DBMS data Model Schema Refinement consistency, normalization Physical Design - indexes, disk layout Security Design - who accesses what, and howConceptual Design What are the entities and relationships in theenterprise? What information about these entities andrelationships should we store in the database ? What are the integrity constraints or businessrules that hold?
Databases Model the Real World ... •Entity: Real-world object, distinguishable from other objects. An entity is described using a set of attributes. •Entity Set: A collection of similar entities. E.g., all employees. –All entities in an entity set have the same set
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