TRANSFORMING THE CONCEPTUAL DATA MODEL TO SQL

TRANSFORMING THE CONCEPTUAL DATA MODEL TO SQL

1. There is a natural evolution from the entity–relationship (ER) data models to a relational schema

2. Rules and SQL Constructs

   • the three types of tables that are produced
     • SQL table with the same information content as the original entity from which it is derived.
     • SQL table with the embedded foreign key of the parent entity.
     • SQL table derived from a relationship, containing the foreign keys of all the entities in the relationship.
   • Binary Relationhsips
     • Both entities mandatories
       • each entity becomes a table, and the key of either entity can appear in the other entity’s table as a foreign key
   • Binary Recursive Relationships
     • A single entity with a one-to-one relationship implies some form of entity occurrence pairing
     • This pairing may be completely optional, completely mandatory, or neither.
     • In all of these cases, the pairing entity key appears as a foreign key in the resulting table.

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