2_Lecture_Notes

2_Lecture_Notes - MIS 380 CLASS 2 What We Are Covering...

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1 CLASS # 2 MIS 380 What We Are Covering Today The Relational Model Primary Keys Entity Relationship Diagrams One to Many Relationships Many to Many Relationships Data Integrity Assignment 1 – 1:N & M:N Relationships
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2 CLASS # 2 MIS 380 The Relational Model METHOD OF REPRESENTING DATA CONCEPTUALLY AS TABLES CALLED RELATIONS WITH SPECIFIC PROPERTIES. DATA MANIPULATION IS DEFINED IN TERMS OF THE MANIPULATION OF THESE TABLES OF DATA. RELATION = TWO-DIMENSIONAL TABLE RELATION IS COMPOSED OF COLUMN HEADINGS (FIELDS, ATTRIBUTES) WITH ROWS OF DATA (RECORDS, TUPLES) ORDER OrderId OrderDate CustomerId 001 010188 1111 002 020389 2222 003 030389 1111 Column = Field = Attribute Row = Record = Tuple Entries within a column have the same data type. More specifically they are defined on the same domain or pool of values Table = Relation
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3 CLASS # 2 MIS 380 The Relational Model ILLEGAL RELATION ID NAME COURSE 1111 JOE MIS380, MIS225 2222 SAM MIS202, MIS420 3333 SALLY MIS380 LEGAL RELATION COURSE TITLE HOURS MIS380 Database I 4 MIS225 Visual Basic 4 MIS420 Systems II 4 Cannot have multiple values in a single cell One value in each cell – this is called First Normal Form (1NF) when a table has no repeating values in a cell TABLE PROPERTIES : EACH CELL CONTAINS A SINGLE VALUE ENTRIES IN A COLUMN ARE OF THE SAME DOMAIN EACH COLUMN HAS A UNIQUE NAME ORDER OF THE COLUMNS AND ROWS HAS NO SIGNIFICANCE NO TWO ROWS ARE IDENTICAL TABLE HAS UNIQUE PRIMARY KEY
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4 CLASS # 2 MIS 380 Primary Keys Primary Key = One or more attributes that uniquely identify each row in the table. Primary keys have four properties: Unique Non-null (not blank) Minimal - use the minimum number of attributes necessary for uniqueness Non-updatable - the value of the primary key should never change - avoid things like names and descriptions that might change over time
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5 CLASS # 2 MIS 380 Unique AND Minimal MEMBER MemberId Email FirstName LastName Phone 1 [email protected] John Day 592-0646 2 [email protected] Thom Luce 592-1111 3 [email protected] Sean McGann 592-2222 MEMBER MemberId Email FirstName LastName Phone 1 [email protected] John Day 592-0646 2 [email protected] Thom Luce 592-1111 3 [email protected] Sean McGann 592-2222 MEMBER MemberId Email FirstName LastName Phone 1 [email protected] John Day 592-0646 2 [email protected] Thom Luce 592-1111 3 [email protected] Sean McGann 592-2222 MEMBER MemberId Email FirstName LastName Phone 1 [email protected] John Day 592-0646 2 [email protected] Thom Luce 592-1111 3 [email protected] Sean McGann 592-2222
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6 CLASS # 2 MIS 380 Database Design Databases are designed as a group of related tables. Entities are like nouns—they are the real-world persons, places or things being modeled in the database—e.g., employees, orders, books Each table is a collection of all the data (attributes) to be stored about a particular entity Relationships are like verbs—they show action or possession—that related one entity to another (e.g., a customer places orders; an employee has dependents; a doctor treats patients and a patient can visit multiple doctors) Relationships can be one to one, one to many, or many to many
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This note was uploaded on 01/24/2011 for the course FIA 111 taught by Professor Matta during the Spring '10 term at Hocking.

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2_Lecture_Notes - MIS 380 CLASS 2 What We Are Covering...

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