Logic Data Modeling 8 - Entity Relationship Diagram, part 1

[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.

[titleistD2]

Your videos are phenomenal, you're lectures come across very clear. However, the only bad is that the "video" quality is so poor you cant read the words on the white board. This makes sometimes difficult to follow, if you would keep on making videos that would be fantastic.

[akshayranalkar1]

amazin lecture..thank you very much

[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.

[anujtyagi1990]

Thank you very much, this video us very helpful for understanding ERD.

[mookjais]

This was outstanding, thanks.

[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.

[iceyscontent]

Great Lecture. Helped A LOT!

[superflex007]

excellent lecture, employing principles of associative learning.

[superflex007]

@superflex007 This is a great lecture, again. I learnt the concept of Cardinality,

then forgot it.

So I came right back here ... to re-learn it !!

Thanks again

[ranabd2002]

Thanks, Very good lecture.

[m0dm0use]

Great video helped on my AIS assignment for creating my ERD + rated

Shame its of fuzzy quality

[leonarbe]

Great video, it helps people learn it much easier this way....

Keep teaching us.... enlighten us!

[Liquidnitrogenheart]

thanks watched this to prep for my bus 141 final:)

[dangermanfears]

how many? MANY :D

[thatnamehasbeentak3n]

Would be great if there wasn't so much glare on the white board - makes it hard to see the diagram :(

Otherwise great video!

[MrDroplick]

Excellent. Very clear and precise example. Thank you!!

[ravirjoshi]

Thanks for the video. It really helps when experts create and upload an educational video like this one. It really helps.

[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.

[tdl0221]

Awesome how you describe the relationships.

[naveen2005kumar]

nice vid. poor disp.

[kedrick87]

nice, but poor lighting...

[dancingtoovercome]

Clear, concise and great examples. Thank you!

[PahnthomCSB]

awesome!!! thank you so much!! :)

[punxz18]

I liked the video but the quality is giving me a hard time :(

[godunjo]

This is an awesome lesson but the camera man needs to upgrade

[csnj100]

it would be nice if camera was focused on the board

[JAFIZRAHMAN]

its a very helpful class.........

[chandiish]

This explanation is simply awesome.......

Really helpful....

All of my doubts got clarified . . . .

[newkool100]

nice...

[sudanthass]

Thanks xD .. i learned ERD from this ti\hing :D

[trade9243]

very very thks u make me pass in exams very very thks ur work is exilent but ur camera man need to improve this work

thks once again

[SchoolSarge]

this guy's good. i wish he'd come out to my uni ;)

[kgeil1971]

Dr. Langer is awesome, he must be a wonderful instructor. I agree with NajanJan that the board writing is not clear, but I'm sure you guys are working with what you've got. Thanks for the great videos.

[NajanJan]

Could you explain what you meant when you said you cover your eyes and pull a record? Does that give you the minimum part of the relationship? could you also give me an example of a (0,n) relationship? thanks

[gvimontslice]

When Dr. Langer refers to looking down on the entity, he's using the metaphor of entities representing physical files as in a paper-base filing cabinet. When we deal with instances of actual records, we are then speaking of records within tables (tables are instantiated entities).

[NajanJan]

Could you tell the difference between (0,n) and (1,n) relationships?

when we say a customer can have 0 or many orders we have (1,n) right? could you give me an example of (0,n)?

Also, when you said you stand on top of that entity and pull up a record, does that have to do with the min number being 0 or 1?

Could you explain that please?

Thanks again for your great videos.

[gvimontslice]

Dr. Langer is using a classic example of the order-items data model. In this case he explains the foundational concept of cardinality. The ERD allows you as a data architect to define the business rules regarding the various permutation of relationships that can exist among entities within the logical data model (remember that entities represent the equivalent of tables within the physical database schema).

[gvimontslice]

Regarding the difference between 0:n and 1:n. With zero or many, the instance of a record within the parent table (entity) of a given relationship is allowed to exist without being forced to have a corresponding instance of a record within the child table (entity).

[gvimontslice]

Specific to this example, the Item table (entity) is allowed to have records that may or may not appear within the Order Items table (entity). As for one or many, the instance of a record within the parent table (entity) of a given relationship is inexorably tied to the existence of at least one matching record within the child table (entity).

[gvimontslice]

Specific to this example, for every record in the Order table (entity), there must exist at least one corresponding recorder within the Order Items table (entity).

[gvimontslice]

To reiterate common data modeling parlance, One and only one Order has one or more Order Items. Likewise, One and only one Item has zero or many Order Items.

[NajanJan]

Thank you for your replies.

I appreciate your time.

[NajanJan]

I'm glad I found your videos here.

I'm starting to learn about data bases and really like it. I guess I will continue my masters in data bases.

thanks for putting these videos :)

[NajanJan]

thanks for the video, but it is not really clear so what you write on the board is not visible but your explanation is good.

[keitaidenwaKern]

nice vids dude. They help a lot.