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cysun
Posts: 2935
Posted 21:48 Sep 28, 2010 |

Please post your solution to the exercise here. The first one who posts the correct solution (both ER diagram and relational schema) will receive some extra credit.

HuanXue
Posts: 34
Posted 22:17 Sep 28, 2010 |

Is it like this?

I got a feel that I will get a great deal of E_mail this quarter....

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ashasabeer
Posts: 55
Posted 00:33 Sep 29, 2010 |
Attached my solution
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cysun
Posts: 2935
Posted 07:57 Sep 29, 2010 |

HuanXue's solution is mostly correct; ashasabeer's solution is wrong.

HuanXue is also correct about getting lots of emails this quarter, especially if you are in both 422 and 520. :)

HuanXue
Posts: 34
Posted 10:32 Sep 29, 2010 |

Only a "mostly" correct? If I want the correct answer, I should visit you or just wait for next class?

PS: there's our textbook on ebay around $50, not very expensive.

cysun
Posts: 2935
Posted 13:18 Sep 29, 2010 |
HuanXue wrote:

Only a "mostly" correct? If I want the correct answer, I should visit you or just wait for next class?

PS: there's our textbook on ebay around $50, not very expensive.

I'll discuss the solution in the next class. And thanks for the information about the textbook.

calikidd
Posts: 41
Posted 14:38 Sep 29, 2010 |

I'm still confused on this.

1.Can't many products have many prices?

There could be multiple products with the same price or a different price, depends on the distribution center, or

2. Should I think about it in that  a product has a price which would make it 1-to-1 right?

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Last edited by calikidd at 15:17 Sep 29, 2010.
cysun
Posts: 2935
Posted 15:21 Sep 29, 2010 |
calikidd wrote:

I'm still confused on this.

1.Can't many products have many prices?

There could be multiple products with the same price or a different price, depends on the distribution center, or

2. Should I think about it in that  a product has a price which would make it 1-to-1 right?

Prices and products should be a many-to-one relationship as in HuanXue's solution.

calikidd
Posts: 41
Posted 16:03 Sep 29, 2010 |

ok, did she need to add the price attribute like this:

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cysun
Posts: 2935
Posted 22:00 Sep 29, 2010 |
calikidd wrote:

ok, did she need to add the price attribute like this:

Yes, obviously the actual price must be stored. There's also a less obvious problem.

calikidd
Posts: 41
Posted 23:24 Sep 29, 2010 |

I am assuming we talk about the less "obvious problem" in class. Is the problem on one of the slides?

Last edited by calikidd at 23:24 Sep 29, 2010.
cysun
Posts: 2935
Posted 10:49 Sep 30, 2010 |
calikidd wrote:

I am assuming we talk about the less "obvious problem" in class.

Yes.

rhardytran
Posts: 8
Posted 23:58 Oct 02, 2010 |

Different idea to approach where product changing every second like stock market.

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cysun
Posts: 2935
Posted 13:49 Oct 03, 2010 |
rhardytran wrote:

Different idea to approach where product changing every second like stock market.

It looks wrong. I don't get why you need two entity sets Price and Market Price.

calikidd
Posts: 41
Posted 15:20 Oct 03, 2010 |
cysun wrote:
rhardytran wrote:

Different idea to approach where product changing every second like stock market.

It looks wrong. I don't get why you need two entity sets Price and Market Price.

 If we wanted to include the market price, wouldn't it just be another attribute for the Price entity?

rhardytran
Posts: 8
Posted 16:06 Oct 03, 2010 |

well, price entity is a look-up value and market price is the actual values of the product occur overtime.  This approach is to just eliminate the duplications of price number/value being stored in the table.  However, we can simplify it by combine both price & market price entities into one entity.

calikidd
Posts: 41
Posted 14:47 Oct 04, 2010 |
rhardytran wrote:

well, price entity is a look-up value and market price is the actual values of the product occur overtime.  This approach is to just eliminate the duplications of price number/value being stored in the table.  However, we can simplify it by combine both price & market price entities into one entity.

 I don't know of any reason to do this, but can we have an attribute that is linked to an entity and a relationship? For instance, the price attribute be linked to the Price entity and the relationship diamond.