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Unit 7: Relational Database Design

7.1 Relational Database Design Notes

The relational model was proposed by E. F. Codd in 1970. It deals with database management
from an abstract point of view. The model provides specifications of an abstract database
management system. To use the database management systems based on the relational model
however, users do not need to master the theoretical foundations.
Codd defined the model as consisting of the following three components:
1. Data Structure: a collection of data structure types for building the database.
2. Data Manipulation: a collection of operators that may be used to retrieve, derive or
modify data stored in the data structures.
3. Data Integrity: a collection of rules that implicitly or explicitly define a consistent database
state or changes of states.
7.2 Features of Relational Database

A good database design has the following features:
1. Faithfulness: The design and implementation should be faithful to the requirements.
(a) The use of constraints helps to achieve this feature.
2. Avoid Redundancy: Something is redundant if when hidden from view, you could still
figure it out from other data. This value is important because redundancy.
(a) Wastes space and
(b) Leads to inconsistency.

3. Simplicity: Simplicity requires that the design and implementation avoid introducing
more elements than are absolutely necessary – Keep it Simple (KIS).
(a) This value requires designers to avoid introducing unnecessary intermediate concepts.

4. Right kind of element: Attributes are easier to implement but entity sets and relationships
are necessary to ensure that the right kind of element is introduced.

7.3 Atomic Domain and First Normal Form

Please see section 7.10 in detail

Task DBMS vs. RDBMS.

7.4 Functional Dependencies

When a single constraint is established between two sets of attributes from the database it is
called functional dependency. We consider a single universal relation scheme “A”. A functional
dependency denoted by XY, between two sets of attributes X and Y that are subset of universal
relation “A” specifies a constraint on the possible tuples that can form a relation state of “A”. The
constraint is that, for any two tuples t and t in “A” that have t (X) = t (X), we must also have
1 2 1 2
t (Y) = t (Y). It means that, if tuple t and t have same values for attributes X then X Y to hold
1 2 1 2
t and t must have same values for attributes Y.
1 2

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