Lecture12

Lecture12 - Databases Comp 101 - Spring 2008 03/26/08 L12 -...

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Comp 101 - Spring 2008 ! 03/26/08 ! L12 - Databases Databases
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Comp 101 - Spring 2008 ! 03/26/08 ! L12 - Databases Not All Tables Are Created Equal Spreadsheets use tables to store data and formulas associated with that data The “meaning” of data is implicit Row and column labels are essentially for decoration, they are not actually linked to the data Spreadsheet tables lack the necessary structure to relate entries in one table to entries in another
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Comp 101 - Spring 2008 ! 03/26/08 ! L12 - Databases Databases • Structured collections of data • Indexed and organized • In contrast to – Files (unstructured) – Spreadsheets (structure but no semantic (meaningful) indexing)
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Comp 101 - Spring 2008 ! 03/26/08 ! L12 - Databases Relational Databases • Specialized tables that describe relationships between data items • Relate the contents of one or more tables • Based on – Properties that are common between tables – Items that are in common • This “structure” allows us to filter and compose data efficiently
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Comp 101 - Spring 2008 ! 03/26/08 ! L12 - Databases Logical Data Model Entities - tables of anything that can be identified by some number of characteristics, called attributes . Attributes have names and values , and these “values” are what is actually stored in a database’s table. Relationships are defined between entities (tables) 846 966 Santa Cruz 76 14 Tower 1494 642 Fernandina 1707 4588 Isabela Elevation Area Name Island Entity Attributes Entity Instance
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This note was uploaded on 11/28/2011 for the course COMP 101 taught by Professor Staff during the Spring '08 term at UNC.

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Lecture12 - Databases Comp 101 - Spring 2008 03/26/08 L12 -...

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