).
The FacultyDegrees entity represents a multivalued attribute. A single faculty member may have multiple
degrees from multiple institutions, and this entity allows us to represent that fact. Finally, the Student entity
shows two subcategories of students, grads and undergrads. An undergrad will have a faculty member serving
as his or her Student Life Advisor, and a grad may (or may not) have a faculty member serving as the chair of
his or her thesis committee.
CHAP. 8] DATABASE 143
Figure 8-2 E-R diagram special cases.
BUILDING A RELATIONAL DATABASE FROM THE DATA MODEL
The data model comprises the conceptual schema, or the description of the structure of the database. This
is one of three schemas, or designs that database developers refer to. The other schemas include the external
schema, which is the database as conceived by the end-users, and the internal schema, which is the set of actual
file structures on disk used by the database management system (SQL Server, Oracle, etc.).
With the conceptual schema created, the next task is to convert the data model into tables, relationships, and data
integrity rules. An entity type is represented as a table, where each row in the table represents an instance of that entity
type.
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