如何改善ERD [英] How to improve a ERD

问题描述

此问题基于我的计划，主题。

我的实体关系图是

alt text http://files.getdropbox.com/u/175564/sequence-diagram.png

我想知道以下内容。

我的序列图是否符合以下关系图？ strong>

alt text http://files.getdropbox.com/u/175564/table-problem-3.png

解决方案

查看第一个图表作为逻辑模型，通常在Logical中定义的表格也存在于物理表格中 - 您缺少QUESTION-TAGS（nee QUESTION-SUBJECTS）表格。您在QUESTION和MONITOR-CHECK之间有一对一的关系，这意味着没有值可以进行MONITOR-CHECK - 将属性移动到QUESTION
表中。

将第二个图视为Physical ERD模型 - 使用具有一对一关系的两个表没有任何好处。我在说的是QUESTION / QUESTION-BODY和QUESTION / MODERATOR-CHECK表。

QUESTION-SUBJECTS命名不当 - tag，然后相应地命名表。此表将是一个代码表（具有CODE，DESCRIPTION列），因为您希望保持查询的值一致以执行良好。也就是说，您需要在QUESTION和QUESTION-TAGS表之间使用一个xref / lookup / corollary表，以便有一个[问题相关]到许多[问题标签]。

QUESTION-ID（pk）

QUESTION-TAG-XREF

CODE（pk）

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

解决方案

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 value to having MONITOR-CHECK - move the attributes into the QUESTION table.

Viewing the second diagram as the Physical ERD model - there's no benefit to having two tables with a one-to-one relationship. I'm speaking about the QUESTION / QUESTION-BODY, and QUESTION / MODERATOR-CHECK tables.

QUESTION-SUBJECTS is poorly named - if by your note the record represents a "tag", then name the table accordingly. This table would be a code table (having CODE, DESCRIPTION columns) because you want to keep the values consistent for queries to perform well. That said, you need an xref/lookup/corollary table between the QUESTION and QUESTION-TAGS table in order to have a one [question related] to many [question tags].

QUESTION-TAG-XREF

• QUESTION-ID (pk)
• QUESTION-TAG-CODE (pk)

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