erd

How to improve a ERD

由 若如初见. 提交于 2019-11-27 07:38:05
问题 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 回答1: 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

How to generate an entity-relationship (ER) diagram using Oracle SQL Developer

由 我与影子孤独终老i 提交于 2019-11-27 02:28:45
I want to use Oracle SQL Developer to generate an ER diagram for my DB tables but I am new to Oracle and this tool. What is the process for creating an ER diagram in SQL Developer? Sergei Mardiyants Create a diagram for existing database schema or its subset as follows: Click File → Data Modeler → Import → Data Dictionary . Select a DB connection (add one if none). Click Next . Check one or more schema names. Click Next . Check one or more objects to import. Click Next . Click Finish . The ERD is displayed. Export the diagram as follows: Click File → Data Modeler → Print Diagram → To Image

Django - Model graphic representation (ERD) [closed]

由 一笑奈何 提交于 2019-11-26 18:58:13
问题 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 回答1: If

When we need to use 1-to-1 relationship in database design?

由 a 夏天 提交于 2019-11-26 14:46:45
问题 When do we need to use a 1-to-1 relationship in database design? In my opinion, if two tables are in a 1-to-1 relationship, they can be combined into one table. Is this true? 回答1: Vertical partitioning for large tables to reduce I/O and cache requirements -- separate columns that are queried often vs rarely. Adding a column to a production system when the alter table is "too expensive". Super-type/subtype pattern. Vertical partitioning to benefit from table (join) elimination -- providing

What mysql database tables and relationships would support a Q&A survey with conditional questions? [closed]

由 谁说胖子不能爱 提交于 2019-11-26 12:36:27
I'm working on a fairly simple survey system right now. The database schema is going to be simple: a Survey table, in a one-to-many relation with Question table, which is in a one-to-many relation with the Answer table and with the PossibleAnswers table. Recently the customer realised she wants the ability to show certain questions only to people who gave one particular answer to some previous question (eg. Do you buy cigarettes? would be followed by What's your favourite cigarette brand? , there's no point of asking the second question to a non-smoker). Now I started to wonder what would be

How to generate an entity-relationship (ER) diagram using Oracle SQL Developer

由 大城市里の小女人 提交于 2019-11-26 12:34:05
问题 I want to use Oracle SQL Developer to generate an ER diagram for my DB tables but I am new to Oracle and this tool. What is the process for creating an ER diagram in SQL Developer? 回答1: Create a diagram for existing database schema or its subset as follows: Click File → Data Modeler → Import → Data Dictionary . Select a DB connection (add one if none). Click Next . Check one or more schema names. Click Next . Check one or more objects to import. Click Next . Click Finish . The ERD is

What mysql database tables and relationships would support a Q&A survey with conditional questions? [closed]

由 Deadly 提交于 2019-11-26 03:02:22
问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 6 years ago . I\'m working on a fairly simple survey system right now. The database schema is going to be simple: a Survey table, in a one-to-many relation with Question table, which is in a one-to-many relation with the Answer table and with the PossibleAnswers table. Recently the customer

How are super- and subtype relationships in ER diagrams represented as tables?

由 ぃ、小莉子 提交于 2019-11-26 00:29:26
问题 I am learning how to interpret Entity Relationship Diagrams into SQL DDL statements and I am confused by differences in notation. Consider a disjoint relationship as in the following diagram: Would this be represented as: Vehicle, 2WD and 4WD tables (2WD and 4WD would point to the PK of Vehicle); or ONLY the 2WD and 4WD tables (and NO Vehicle table), both of which would duplicate whatever attributes Vehicle would have had? I think these are other ways of writing the relationship: I\'m looking
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