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1-4 RELATIONAL DATABASES & NORMALIZATION (NORMALIZATION (Objectives…
1-4 RELATIONAL DATABASES & NORMALIZATION
A relational database
STORES
info in tables with rows & columns
Table = collection of records
Row =
RECORD
/ instance
Column =
Field
/ attribute
Advantages
Avoids
duplication of data
Ensures
consistency of the data that is stored as records
Easier to
modify
data and data format
Easier to
insert
and
delete
data
NORMALIZATION
Process
of
organizing
the attributes and tables of a relational database
to minimize redundancy
Helps
in
handling
INSERT, UPDATE, AND DELETE anomalies, ENSURING a better performance of the database
Objectives
To
make
the relational model more
informative
to users
To
make
the collection of tables neutral to the query statistics,
To
free
the collection of tables from
undesirable
insertion, update, and deletion dependencies
To
reduce
the need for restructuring the collection of relations
Partial dependency
Exist when there is a functional dependence in which the determinant is only part o the primary key
Transitive dependency
Exist when there are functional dependencies such that X -> Y, Y - > Z, and X is the primary key
Dependency Diagram
Depicts all dependencies found within given table structure
Helpful in getting bird's-eye view of all relationships among table attributes