Lecture 7 - Introduction to DBs - annotated

Lecture 7 - Introduction to DBs - annotated - What is...

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1 Introduction to relational databases INFO/COM S 230: Intermediate Web Design and Programming What is…? A database is a collection of related data. A database management system (DBMS, database system) is a piece of software used to manage a database efficiently, so that it will persist safely over long periods of time. The data in the table is certainly a database. But the program isn’t a DBMS. Why not? A DBMS… • Allows for persistent storage of very large amounts of information, and efficient access to it. • Implements a “query language” (SQL) to store, access, and modify the data. • Can enforce that the stored data is consistent in certain ways. • Allows for concurrent access by many users. Why? Why might we prefer to use a DBMS to writing our own program for database access? DBMSes already exist; don’t have to write things from scratch (especially tricky things like concurrent access, recovering from crashes, etc.) Don’t need to think about how data is stored; a simple interface via SQL (i.e. no worrying about file format – are we using \t as a delimiter??) Can write quite powerful queries very simply via SQL; don’t need to write a program for each one. Security; allowing only some users access to some data. Easy PDF Creator is professional software to create PDF. If you wish to remove this line, buy it now.
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2 A running example: Movies Data associated with a movie: A running example: Movies • Title • Genre • Year • Actors/Actresses • Director • Producer • Movie studio • … Relational databases Why “relational”? The data is organized in
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This note was uploaded on 04/01/2008 for the course INFO 2300 taught by Professor Williamson during the Spring '08 term at Cornell.

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Lecture 7 - Introduction to DBs - annotated - What is...

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