Comments on: Logic Data Modeling 8 – Entity Relationship Diagram, part 1 http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/ My blog - my rules. Wed, 30 Nov 2011 14:15:24 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: NajanJan http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105670 NajanJan Mon, 08 Mar 2010 08:57:54 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105670 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. 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.

]]> By: NajanJan http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105669 NajanJan Mon, 08 Mar 2010 08:36:38 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105669 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 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

]]> By: gvimontslice http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105668 gvimontslice Mon, 08 Mar 2010 08:05:13 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105668 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). 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).

]]> By: gvimontslice http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105667 gvimontslice Mon, 08 Mar 2010 07:26:45 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105667 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). 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).

]]> By: gvimontslice http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105666 gvimontslice Mon, 08 Mar 2010 06:33:40 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105666 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). 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).

]]> By: gvimontslice http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105665 gvimontslice Mon, 08 Mar 2010 06:31:31 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105665 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). 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).

]]> By: gvimontslice http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105664 gvimontslice Mon, 08 Mar 2010 06:05:38 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105664 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. 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.

]]> By: gvimontslice http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105663 gvimontslice Mon, 08 Mar 2010 05:47:39 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105663 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). 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).

]]> By: kgeil1971 http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105662 kgeil1971 Mon, 08 Mar 2010 05:27:46 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105662 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. 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.

]]> By: SchoolSarge http://blog.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/comment-page-1/#comment-105661 SchoolSarge Mon, 08 Mar 2010 04:36:39 +0000 http://www.jellofart.com/logic-data-modeling-8-entity-relationship-diagram-part-1/#comment-105661 this guy's good. i wish he'd come out to my uni ;) this guy’s good. i wish he’d come out to my uni ;)

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