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transitive dependency

Posted on 2003-11-11
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Im confused by what this is, arent they the same thing??
       
      
partial functional dependency
Description       
In database terminology, a partial functional dependency occurs when the value in a non-key attribute of a table is dependent on the value of some part of the table's primary key (but not all of it).

       
transitive dependency
Description       
A transitive dependency occurs in a database table when the value of a non-key attribute is dependent on the value of another non-key attribute in that table.

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Question by:illucid
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yoren earned 125 total points
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No. Here's an example with both a transitive dependency and a partial functional dependency. Key is SID/Major -- this student has a double major

SID      Major            School            Maj_GPA            School_Location
123      Physics            Engineering      4.0            EngTown
123      Music            Arts            3.3            Artsville

Transitive dependency: School *determines* School_Location (School is not a key)
Partial functional dependency: Major determines School (Major is part of the key)

Now, remove the partial functional dependency:

SID      Major            Maj_GPA      
123      Physics            4.0            
123      Music            3.3      

Major      School            School_Location
Physics      Engineering      EngTown
Music      Arts            Artsville


Still have a transitive dependency. Now remove that:


SID      Major            Maj_GPA            
123      Physics            4.0            
123      Music            3.3            

Major      School
Physics      Engineering
Music      Arts

School            School_Location
Engineering      EngTown
Arts            Artsville


...and you're in 3rd normal form.
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