erd

Database design - ERD. Modeling Question

由 北慕城南 提交于 2019-12-01 06:09:33
问题 Hopefully someone may be able to quickly advise the best way for me to model my ERD (I'm using IDEF1X & ERWin not Chen Notation) although it doesn't really matter. Basically I have Three Entities Organisation Person Trustee Business rules state that a Trustee can be either a person or organisation. My question is, would it be correct to have two primary, foreign key relationships to Trustee. One from Organisation > Trustee and the second from Person > Trustee. Where one of the FK fields of

How to export/save ERD as PDF or as image in phpMyAdmin?

由 谁说我不能喝 提交于 2019-12-01 04:43:40
问题 I have generated an ERD using the Designer in phpMyAdmin. How do I save it as PDF or image? On possible duplicate: The "original" thread is referenced in the answer. This post is intended to be a visual tutorial thread with screenshots which the other thread does not have. 回答1: To save as PDF: 1) Select databse. 2) More > Designer 3) Import/Export coordinates for relational schema 4) Operations (scroll down) > Edit or export relational schema Click Go. 5) Choose your preferences. Click Go.

Trying to understand cardinality in an entity relationship diagram?

由 僤鯓⒐⒋嵵緔 提交于 2019-12-01 00:39:42
I'm quite new to relational databases and have been having a lot of trouble recently trying to understand an entity relationship diagram I've been given. Here it is: Solicitor ERD (ERD is for a made up solicitor company) Basically my task is to take this ERD and write an SQL script to create the database, obviously filling in the tables with data I can make up. The SQL syntax isn't the thing I'm having a hard time with, it's simply understanding the cardinality in the diagram. To me the terms '1 to 1', '1 to many', 'many to many' just don't click, I have no idea what they mean and how they

When to use UML Association Classes?

由 北战南征 提交于 2019-11-30 09:09:01
Can I improve my design on these 2 diagrams below? If so, how? I am confused by the use of association classes in my diagrams. Should I use them? Figure 1 Figure 2 For association classes, they make sense only if they represent associations with some behaviour and state. Look at Article'sSubject. It has nothing more than source, target and identity. You don't need a class for such a association, just use plain association, which has all those properties. There are more such unnecessary association classes in your diagrams. Another important thing when using association classes is that every

How to identify a strong vs weak relationship on ERD?

由 不羁岁月 提交于 2019-11-29 20:19:06
A dashed line means that the relationship is strong, whereas a solid line means that the relationship is weak. On the following diagram how do we decide that the relationship between the Room and Class entities is strong. Is it because Room entity has a regular key (non-composite)? We draw a solid line if and only if we have an ID-dependent relationship; otherwise it would be a dashed line . Consider a weak but not ID-dependent relationship; We draw a dashed line because it is a weak relationship. Weak (Non-Identifying) Relationship Entity is existence-independent of other enties PK of Child

How to identify a strong vs weak relationship on ERD?

由 戏子无情 提交于 2019-11-28 16:18:49
问题 A dashed line means that the relationship is strong, whereas a solid line means that the relationship is weak. On the following diagram how do we decide that the relationship between the Room and Class entities is strong. Is it because Room entity has a regular key (non-composite)? 回答1: We draw a solid line if and only if we have an ID-dependent relationship; otherwise it would be a dashed line . Consider a weak but not ID-dependent relationship; We draw a dashed line because it is a weak

How to improve a ERD

由 风流意气都作罢 提交于 2019-11-28 13:01:45
This question is based on my plan at the thread . My entity-relationship diagram is alt text http://files.getdropbox.com/u/175564/sequence-diagram.png I would like to know the following. Does my sequence diagram match the following relation diagram? alt text http://files.getdropbox.com/u/175564/table-problem-3.png Reviewing the first diagram as the Logical model, typically the tables defined in the Logical also exist in the physical - you're missing the QUESTION-TAGS (nee QUESTION-SUBJECTS) table. You have a one-to-one relationship between QUESTION and MONITOR-CHECK, which means there's no

Database design and modeling specific relationships

由 北战南征 提交于 2019-11-28 12:50:39
问题 I am trying to implement a shipping and tracking solution. There are TRUCKS that move PRODUCTS from a CITY to another CITY via designated PATHS on specific SCHEDULES . The TRUCKS transport the PRODUCTS via CONTAINERS . These TRUCKS are instructed via JOBS , like pick_up , transfer , drop_off . The problem that I am having is when product_1 needs to be moved by truck_1 via a pick_up JOB from city_A to city_C via city_B . At the same time, there is product_2 being moved by truck_2 via a JOB of

product with multiple category type database schema

由 和自甴很熟 提交于 2019-11-27 23:10:29
问题 I want to store information about song files which they are categorized by: 1. genre for example: pop, rock, classical etc. 2. instrument used like piano violinn etc 3. Artist Each song has many instruments. Each song has many artist. So all of the relations are many-to-many. How can I implement this? Is it good idea to make many-to-many relation between song entity and those three category type entities? or should I only have a single category entity that inherits those sub categories?

Django - Model graphic representation (ERD) [closed]

由 孤者浪人 提交于 2019-11-27 17:16:56
I'm searching a way to represent my Django project model graphically. Is there some application that does this kind of ERD (diagram) ? Update following @Etienne instructions Here is an example of how I finally view the PDF representing some models of my django project $ python manage.py graph_models app1 app2 ... | dot -Tpdf | evince It actually generates the dot data with my applications (app1, app2, ...) Passes the result to dot to output into PDF format Opens the output with evince Etienne If you want to extract UML diagram from your Django models you can use the Graph models command of
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