1. 

   MrDroplick
   March 7th, 2010 - 21:11

   Excellent. Very clear and precise example. Thank you!!
2. 

   ravirjoshi
   March 7th, 2010 - 21:45

   Thanks for the video. It really helps when experts create and upload an educational video like this one. It really helps.
3. 

   naveen2005kumar
   March 7th, 2010 - 21:47

   nice vid. poor disp.
4. 

   Untouchab1e
   March 7th, 2010 - 22:26

   Very good, although the video quality is so bad I cant see what he’s writing..
5. 

   kedrick87
   March 7th, 2010 - 23:02

   nice, but poor lighting…
6. 

   dancingtoovercome
   March 7th, 2010 - 23:46

   Clear, concise and great examples. Thank you!
7. 

   PahnthomCSB
   March 7th, 2010 - 23:49

   awesome!!! thank you so much!!
8. 

   punxz18
   March 8th, 2010 - 00:24

   I liked the video but the quality is giving me a hard time
9. 

   godunjo
   March 8th, 2010 - 01:11

   This is an awesome lesson but the camera man needs to upgrade
10. 

    csnj100
    March 8th, 2010 - 01:56

    it would be nice if camera was focused on the board
11. 

    JAFIZRAHMAN
    March 8th, 2010 - 02:01

    its a very helpful class………
12. 

    chandiish
    March 8th, 2010 - 02:43

    This explanation is simply awesome…….
    Really helpful….
    All of my doubts got clarified . . . .
13. 

    newkool100
    March 8th, 2010 - 02:59

    nice…
14. 

    sudanthass
    March 8th, 2010 - 03:42

    Thanks xD .. i learned ERD from this tihing
15. 

    trade9243
    March 8th, 2010 - 04:03

    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
16. 

    SchoolSarge
    March 8th, 2010 - 04:36

    this guy’s good. i wish he’d come out to my uni
17. 

    kgeil1971
    March 8th, 2010 - 05:27

    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.
18. 

    gvimontslice
    March 8th, 2010 - 05:47

    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).
19. 

    gvimontslice
    March 8th, 2010 - 06:05

    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.
20. 

    gvimontslice
    March 8th, 2010 - 06:31

    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).
21. 

    gvimontslice
    March 8th, 2010 - 06:33

    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).
22. 

    gvimontslice
    March 8th, 2010 - 07:26

    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).
23. 

    gvimontslice
    March 8th, 2010 - 08:05

    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).
24. 

    NajanJan
    March 8th, 2010 - 08:36

    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
25. 

    NajanJan
    March 8th, 2010 - 08:57

    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.

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