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10-21-07, 05:41
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Registered User
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Join Date: Oct 2007
Posts: 10
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Desperate ERD Help!
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Hi
Basically Im having trouble with an Entity Relationship Diagram (ERD), for an assignment. The ERD is based on a simple scenario, I have attempted it a few times and the lecturer says its not right.
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Last edited by JIM1974 : 10-21-07 at 11:13.
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10-21-07, 07:16
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SQL Consultant
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Join Date: Apr 2002
Location: Toronto, Canada
Posts: 13,556
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what's wrong with the part in red, in your own words?
where are your constraints? (primary keys and foreign keys)
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10-21-07, 08:26
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Registered User
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Join Date: Oct 2007
Posts: 10
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HI There
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Thanks for taking a look.
Below is a link to a updated erd with all the attributes and primary/foreign keys.
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Last edited by JIM1974 : 10-21-07 at 11:13.
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10-21-07, 08:39
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SQL Consultant
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Join Date: Apr 2002
Location: Toronto, Canada
Posts: 13,556
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Quote:
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Originally Posted by JIM1974
... she was not happy with the skilled vehicle drivers entity
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neither am i
in words, what does one instance of this entity represent? what is that pk made of? it looks like it might be an auto_increment, and generally speaking, you should never have an auto_increment for a relationship table
see what you can do if that table were completely eliminated
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10-21-07, 09:02
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Registered User
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Join Date: Oct 2007
Posts: 10
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Hi Again
sorry about the basic diagram dont have access to proper ERD design tool at home.
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Last edited by JIM1974 : 10-21-07 at 11:14.
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10-21-07, 09:09
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Gives Bad Advice
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Join Date: Mar 2007
Location: 010101010110100
Posts: 706
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One would think that colleges could sure come up with better real life examples to model. ..driver skill?? I personally don't see where that ties into an order. 
__________________
I and many others around the world are of the strong belief that the universe was created by the Flying Spaghetti Monster. It was He who created all that we see and all that we feel. We feel strongly that the overwhelming scientific evidence pointing towards evolutionary processes is nothing but a coincidence, put in place by Him.
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10-21-07, 09:19
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Registered User
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Join Date: Oct 2007
Posts: 10
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fjm1967
Do you have any sudgestions?
Basically i just want a quick solution so i can get the schema finished and build for oracle database and get the assisgnment out the way.
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Last edited by JIM1974 : 10-21-07 at 09:24.
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10-21-07, 09:26
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Gives Bad Advice
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Join Date: Mar 2007
Location: 010101010110100
Posts: 706
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I can give you my opinions about your model but r937 is the one you want to listen to.
Do you have the option of totally removing the skill entity or did your instructor tell you that you had to have it? I don't understand what driver skill has to do with an order.
__________________
I and many others around the world are of the strong belief that the universe was created by the Flying Spaghetti Monster. It was He who created all that we see and all that we feel. We feel strongly that the overwhelming scientific evidence pointing towards evolutionary processes is nothing but a coincidence, put in place by Him.
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10-21-07, 09:34
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Registered User
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Join Date: Oct 2007
Posts: 10
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Basically the instructor gave the scenario and the entitys
Then we have to come up with a working model
But i would be happy for any input you could offer me.
I do appriciate time given.
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Last edited by JIM1974 : 10-21-07 at 11:14.
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10-21-07, 09:36
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Gives Bad Advice
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Join Date: Mar 2007
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Ok, I will give you my take on how it should be based on what your instructor said. brb.
__________________
I and many others around the world are of the strong belief that the universe was created by the Flying Spaghetti Monster. It was He who created all that we see and all that we feel. We feel strongly that the overwhelming scientific evidence pointing towards evolutionary processes is nothing but a coincidence, put in place by Him.
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10-21-07, 09:50
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Gives Bad Advice
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Join Date: Mar 2007
Location: 010101010110100
Posts: 706
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This is how I would model it. I would remove the three entities you have for the special vehicles. You can use the vehicle type column in the vehicle entity to track that.
Quote:
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particular skills are not necessarily associated with a vehicle, however; the drivers’ skills information is used merely as a guide to driver allocation at present.
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Because of this, I simply associated the chauffer's skill set with the driver. I am assuming that the "skilled vehicle driver" entity is only a record of the skill levels that a driver can have.
__________________
I and many others around the world are of the strong belief that the universe was created by the Flying Spaghetti Monster. It was He who created all that we see and all that we feel. We feel strongly that the overwhelming scientific evidence pointing towards evolutionary processes is nothing but a coincidence, put in place by Him.
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10-21-07, 09:59
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SQL Consultant
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Join Date: Apr 2002
Location: Toronto, Canada
Posts: 13,556
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Quote:
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Originally Posted by JIM1974
Basically i just want a quick solution
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you are not going to get that here
we do not do homework assignments
however, we will help you do yours by asking you questions
you still have to do all the work, though
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10-21-07, 10:03
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Gives Bad Advice
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Join Date: Mar 2007
Location: 010101010110100
Posts: 706
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oops.. I missed that.. 
__________________
I and many others around the world are of the strong belief that the universe was created by the Flying Spaghetti Monster. It was He who created all that we see and all that we feel. We feel strongly that the overwhelming scientific evidence pointing towards evolutionary processes is nothing but a coincidence, put in place by Him.
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10-21-07, 10:04
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Registered User
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Join Date: Oct 2007
Posts: 10
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Cheers fjm1967
I understand your solution to the scenario.
Does anybody else agree or disagree with fjm1967 opionion's to my model or anythink else they can add.
r937 what do you think?
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10-21-07, 10:10
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Registered User
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Join Date: Oct 2007
Posts: 10
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Cool thats fine with me.
Ive been at it for 3 weeks and i was only really asking for asistance, I learn through examples and this is the first one ive attempted.
In my oppion data modeling is not clear cut. Its more on the oppions of erd designer. That is basically what i was asking for.
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Last edited by JIM1974 : 10-21-07 at 10:14.
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Desperate ERD Help!
