Logic Data Modeling 8 - Entity Relationship Diagram, part 1

Lecture by Dr. Art Langer, author. Analysis & Design of Information Systems (3nd Ed), Langer, Springer-Verlag 2007 (ISBN978-1-844628-654-4)

Category:

Education

Tags:

• Logical
• Data
• Modeling
• Normalization
• Database
• Design

[midpitts]

On the Logic Data Modeling 8 - Entity Relationship Diagram, part 1 there was something at the very end that I didn't understand. What did the 2 "1" or lines you put accross the relatonship between the orders and customers (closest to the customers entity) mean. I really have learned a lot from your videos. Thanks for taking the time to provide them to us.

[gvimontslice]

@midpitts We use crows foot notation to indicate cardinality among entities, simply put, degrees of participation. Crows foot notation tells us the minimum and the maximum degree of participation. The | pipe symbol represents “one”. The double pipe || is read as one and only one, a minimum of one and a maximum of one. The “less-than” & “greater-than” symbol is used to indicate “many”. Example: [Customer]-||--------|<-[Order­]; this is read as one and only one customer has one to many orders.

[hisindeweni1977]

great lecture there but too fast . i had trouble using my SQL server as it made me use up all my time today. why is the lecture not using the computer screen. the board is too complicated to use.

[gvimontslice]

@hisindeweni1977 - Mastering the skills of normalization and modeling data logically begins with pencil, paper and your head. If you can't work this out without a special tool, you're already focusing on the wrong problem. Any tool, be it a modeling tool or a physical database will only help you to more quickly express that which you know about cardinality, relationships and referential integrity. Focus on mastering the meaning of 1NF, 2NF and 3NF; then move on to using the database tools.

[tdl0221]

In the OrderItems table, why is (OrderNum ItemNum) a single primary key? Shouldn't it be two primary foreign keys for OrderItems table? (OrderNum(PF) and ItemNum(PF)

[gvimontslice]

Both data elements are listed together as a concatenation (or a compound primary key). Remember that this ERD is a logical data model and does not necessarily represent the physical data model. In this case, Order Number PK-FK and Item Number PK-FK are simply listed together as a matter of convenience.

[dashyou]

Thank you for the great videos Dr. Langer!! helped me prepare for my interview in a short time!!

[ChevailerNoir]

You have just taught me in less than 10 minutes what my teacher has been trying to teach me for a week. You. Are. Awesome! Thank you!

[kalaisdb]

This video helped me a lot to understand normalization. I read many articles related to normalization but i was not able to follow them. This video gave me a clear picture of normalization. Thank you very

[MrSoftcon]

#awsum!! thanx

[bestVirtualteacher]

best., great, awe sum, tremendous

and what can i say you are a best teacher

[AAR4010]

You explained this so much better than my tutor! Thanks!

[romero1337]

thanks for being so clear, and easy to understand, uve taken away any doubts i had about ERDs

[Blizzworks]

Hehe Feeling like im back at university even though im on holiday from it. Love it great presentation and awesome explination of whats going on thank you for helping! Will recommend this!

[kalabash14]

Amazing explanation..



[Ryangosden]

Very nice explanation, thanks. Like a previous user stated, if the quality could be a little clearer it would be great.