Chapter 10 \"NEED HELLLLLLLLPPPPPPPPPPPP!!!!!!!!!! How to design a database Exer

Question

Chapter 10 "NEED HELLLLLLLLPPPPPPPPPPPP!!!!!!!!!!

How to design a database

Exercises

1. Create a database diagram that shows the relationships between the seven tables in the MyGuitarShop database. (The administrators table is not related to the other six tables.)

2. Design a database diagram for a database that stores information about the downloads that users make.

Each user must have an email address, first name, and last name.

Each user can have one or more downloads.

Each download must have a filename and download date/time.

Each product can be related to one or more downloads.

Each product must have a name.

Explanation / Answer

2)

It isn't at all clear what the intention is here. I can see that you have at least three entities here - Users, Products and Downloads. The Users and Products simply store the attributes of he underlying object - the names and for the user, the email address. Downloads clearly references Users and has the datestamp attribute.

What isn't clear is how Downloads relate to Products and how filenames relate to either. I can see two principal possibilities here - a Product consists of a single file in which case Downloads would reference Products, and Products would hold the filename.

The other alternative is that a Product is composed of multiple files, in which case Files would become a fourth entity, holding the filename and referencing Products to indicate which it is associated with. Downloads would then in turn reference Files.

In short, your textual description isn't quite complete. That isn't unusual, EER diagrams exist in part to highlight these very shortcomings early in the design phase.

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