>I have done the table of Class,Subclass,Order,suborder,SuperFamily,
>Family,SubFamily with referential integrity.
>Now I have supposed that the subclass & Suborder could be also not
>present, thus I have linked in the Table Class the Order
>and also the Subclass..
 
The only "required" ranks are Phylum, Class, Order, Family, and Genus. A
database structure that avoids the problem of missing ranks is a
"parent-child" format. This allows you to point a name to the next name in
the hierarchy regardless of its rank.
 
Child           Parent
 
Caenogastropoda Gastropoda
Cypraea         Cypraeinae
Cypraeinae      Cypraeidae
Cypraeidae      Cypraeoidea
Cypraeoidea     Neotaenioglossa
Gastropoda      Mollusca
Neotaenioglossa Caenogastropoda
Trivia          Triviinae
Triviinae       Triviidae
Triviidae       Cypraeoidea
 
One can add a column to specify the rank of the child. The problem with this
structure is that one must know how to do a query with a variable number of
loops. That is, for one genus, five loops through the table might be needed
to get to the class, for another, it might take eight loops. One can also go
the opposite direction, for example, pulling a list of all the genera in a
superfamily.
 
Gary
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Gary Rosenberg, Ph.D.                     [log in to unmask]
Malacology & Invertebrate Paleontology    gopher://erato.acnatsci.org
Academy of Natural Sciences               http://www.acnatsci.org
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