cs411-02-er - CS411 Database Systems 02: ER Model 1...

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1 CS411 Database Systems 02: ER Model
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Announcements • Next Tuesday (8/30/11) – Prof. Jiawei Han will give the lecture • Second part of ER model and first part of relational model • Next Thursday (9/1/11) – Our TA Reza Shiftehfar will give the tutorial on project overview 2
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Why Do We Learn This? • High-level design phase – What information will be stored? – How information elements will be related to one another? – What constraints should be assumed? – ER model is a conceptual data modeling language to help you express your data and your thoughts about the data 3
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Review: Overall Picture of the Course User perspective – how to use a database system? – conceptual data modeling , the relational and other data models, database schema design, relational algebra, and the SQL query language. System perspective – how to design and implement a database system? – data representation, indexing, query optimization and processing, transaction processing, concurrency control, and crash recovery 4
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5 Steps in Building a DB Application • Suppose you are working on CS411 project • Step 0: pick an application domain – we will talk about this later • Step 1: conceptual design – discuss with your team mates what to model in the application domain – need a modeling language to express what you want – ER model is the most popular such language – output: an ER diagram of the app. domain
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6 Steps in Building a DB Application • Step 2: pick a type of DBMS – relational DBMS is most popular and is our focus • Step 3: translate ER design to a relational schema – use a set of rules to translate from ER to rel. schema – use a set of schema refinement rules to transform the above rel. schema into a good rel. schema • At this point – you have a good relational schema on paper
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7 Steps in Building a DB Application • Subsequent steps include – implement your relational DBMS using a "database programming language" called SQL – ordinary users cannot interact with the database directly – and the database also cannot do everything you want – hence write your application program in C++, Java, Perl, etc to handle the interaction and take care of things that the database cannot do • So, the first thing we should start with is to learn ER model . ..
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8 ER Model • ER model: the Entity-Relationship model – The structure of data is represented as an ER diagram • Gives us a language to specify – what information the db must hold – what are the relationships among components of that information • Proposed by Peter Chen in 1976 • What we will cover – basic concepts – constraints – weak entity sets – design principles
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Basic Concepts • Entity sets • Attributes • Relationships 9
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10 Entity Sets • Entities – real-world objects distinguishable from other objects – Examples: • Each product (e.g., ipad2) is an entity • Each company (e.g., Apple) is an entity • Entity set: a collection of similar entities
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This note was uploaded on 02/17/2012 for the course CS 411 taught by Professor Winslett during the Fall '07 term at University of Illinois at Urbana–Champaign.

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cs411-02-er - CS411 Database Systems 02: ER Model 1...

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