Crowfeet on both ends indicate a many-to-many relationship.
ammoQ
2009-05-29 07:56:43
+1
A:
It depends on tyhe notation you are using but typically:
- the crowsfoot (arrow) indicates many
- the black dot indicates required
- the white dot indicates optional
Note that just because a diagram is drawn doesn't makes the relationships it shows sensible, or even possible.
anon
2009-05-29 08:04:38
"Note that just because a diagram is drawn doesn't makes the relationships it shows sensible, or even possible." -> Do you mean that it's simply a visual representation but there's no verification of whether it makes good sense as a database schema?
eggdrop
2009-05-29 08:15:03
The strange thing is that, now that I understand what the symbols mean, the generated diagram does not seem to reflect the underlying schema at all. Maybe there's something wrong with the tool.
eggdrop
2009-05-29 08:20:15
If you extracted it from a database schema, it should normally reflect the schema. Of course, not all schemas make sense from a business perspective, indeed I suspect the majority do not.
anon
2009-05-29 08:22:01
"not all schemas make sense from a business perspective, indeed I suspect the majority do not" - you mean just because people have difficulty designing schemas effectively for business or because the emphasis in schema design is on technical considerations rather than business needs? Not sure I follow. Wouldn't it be quite a problem for a large number of businesses if what you said is true?
eggdrop
2009-05-29 08:32:22
It IS a problem. Most business have enormous problems mapping their business processes onto database schema.
anon
2009-05-29 08:36:12
+2
A:
- One Category can have many CategorySections, but one CategorySection can belong to one Category.
- One Categorization can have many Categories, but one Category can belong to only one Categorization.
- A Categorization can have many CategorySections and a CategorySection can belong to many Categorizations.
I think it tells someting like you can create many different categorizations that define different categories but categorysections can be shared among the different categories (and categorizations).
Vizu
2009-05-29 08:05:19