Data Management and Development Notes

Data can only have one to many rela9onships data must

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Unformatted text preview: ela9onships within the database Data rela9onships •  One- to- many rela9onships –  Example: A painter may paint many pain9ngs, but each pain9ng is only painted by one painter •  Many- to- many rela9onships –  Example: A student may take many courses and each course can be taken by many students •  One- to- one rela9onships –  Example: A salesperson is assigned to a company car Evolu9on of database models •  Hierarchical model –  Rela9onships between the data must fit an upside- down “tree” or “parent- child” structure. –  Data can only have one- to- many rela9onships –  Data must always be retrieved from the top down –  Not flexible Final Assembly Component A Part 1 Part 2 Component B Part 3 Evolu9on of database models •  Network Model –  Allows “child” to have more than one “parent” –  More flexible than the hierarchical model but difficult to design and use properly –  Very complex for programming Component A Part 1 Component B Part 3 Part 2 Fi_ng 1 Fi_ng 2 Fi_ng 3 Evolu9on of database models •  Rela9onal Model –  Developed by E.F. Cobb in 1970 (IBM) –  It revolu(onized database design and prac9ce –  Conceptually simple –  Easy for end users to construct queries and retrieve data on an ad- hoc basis Rela9onal database model •  The database is a collec9on of tables or rela9ons –  Each column in the table is a field or acribute –  Each row in the table is a record Table Name: Student StudentID LName FName Email 3456789 Lin Rose rlin...
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This document was uploaded on 02/14/2014.

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