Information Technology Reference
In-Depth Information
Step 6—Draw EER model.
As a result of the previous steps, an EER model can be drawn, as shown in
Fig.
3.24
.
The following steps map the derived EER model into a relational schema:
Step 1—Map entities into relations.
Each entity can be translated into a relation as shown below:
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Step 2—Map m:n relationships into relationship relation.
In this example, the relation Section is derived as follows:
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Step 3—Map aggregation into relation.
As relationship relation Section is related to entity Student in an m:n relation-
ship, there is an aggregation relation as follows:
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As a result of the previous steps, the derived relations can be merged as follows:
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3.4
Indirectly Translating a Hierarchical Model
into a Relational Model
Since the hierarchical model can be taken as subset of the network model, the proce-
dure for translating a hierarchical schema into relational is similar to the procedure
of translating network schema into relational except for the following steps:
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