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sqlonthefly
Starting Member
1 Post |
 Posted - 2008-03-21 : 23:26:58
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| Hi,A Composite entity can be made out of two Primary Keys (PK) of two different entities. Therefore it can be called as a link table. Therefore the composite entity depends upon the other two entites. Therefore the composite entity is a exsitence dependent on the other two entities. Therefore do every composite is a weak entity?TY |
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SwePeso
Patron Saint of Lost Yaks
30421 Posts |
Posted - 2008-03-22 : 05:00:48
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Therefore what?
E 12°55'05.25"N 56°04'39.16" |
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jsmith8858
Dr. Cross Join
7423 Posts |
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TG
Master Smack Fu Yak Hacker
6065 Posts |
Posted - 2008-03-22 : 09:53:39
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| not sure I understand the question either but I think I do...Is every row in a link table (or association table) considered to be a "weak entity" ?I'm guessing: "yes".Accoring to wikipedia:http://en.wikipedia.org/wiki/Weak_entityhttp://en.wikipedia.org/wiki/Associative_entityaccoring to the link above:"There are two types of weak entities associative entities and subtype entities."your "link" (or "assoication") table I believe falls into the prior category.EDIT:Now if your question is:Is every entity whose primary key is a composit of foreign keys to other entities considered a "weak entity"?Then I would say, "no".It would only be the "sub-type" category (order/lineitme) or the associative category which is designed to support many-to-many relationships.Be One with the OptimizerTG |
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The difference between composite and weak entities