Homework_3_Solution_revised

# Homework_3_Solution_revised - Homework 3 Solution ISE 382...

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Homework 3 Solution ISE 382 Spring 2006 A Assume that Marcia keeps a table of data about her customers. Consider just the following part of that table: CUSTOMER (Phone, FirstName, LastName) Explain the conditions under which each of the following are true: 1. Phone (FirstName, LastName) 2. (Phone, FirstName) LastName 3. (Phone, LastName) FirstName 4. (LastName, FirstName) Phone 5. Phone  LastName 6. Phone  FirstName 7. Phone  (FirstName, LastName) Is condition 7 the same as conditions 5 and 6? Why or why not? 1. Phone (FirstName, LastName) To answer function dependency questions remember this – If A -> B, then each value of A will be paired with one and only one value of B. A particular value of A may appear more than once in a relation, but if so, it is always paired with the same value of B. Note that the reverse is not necessarily true. If A - > B, then a value B may be paired with many values of A. Phone -> FirstName This is true if each phone is paired with only one first name. However, a firstname can have multiple phones Phone -> LastName

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Homework_3_Solution_revised - Homework 3 Solution ISE 382...

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