Relational Database Theory
In 1970 a
mathematician Edgar F. Codd, published the concept that would allow people to
access information from databases without having to know how they are structured.
Common relational database software are Microsoft Access and Oracle.
To
understand the basic concepts there are a few key terms to identify. A database
can be defined as one that contains one or more tables of information. The rows
within a table are referred to as records
and the columns are referred to as
fields or attributes. A
relational database requires two or more related tables. Sometimes in order to
increase efficiency and reduce error normalizing
data is required. This involves dividing information into multiple tables that
are organized differently so that there is not redundant information. Primary keys are values within a field
that are composed of all unique values. For instance if a table has fields: student
identification number, age, and degree. The primary key in this case is student
identification number because there is not repeated value, each student has a
unique identification number. When normalizing data the tables are structured
as either parent, child, or orphan. When two tables have an unequal
relationship, the independent one is referred to as the parent and the dependent one is the called the child. However, if there a record within the child table that does
not appear in the parent table, that record is called an orphan. The number of records in one table that can be related to
the records of another is table is identified as cardinality.
The major advantage and use of relational models is
its uniformity. All value stored in a table is organized to comply with the
same structure. That is each record (row) are formatted the exact same.
However, the fields can be unique to each primary key. Additionally, data is
only stored once and allows for more efficient storage of information. It also
allows for better security since data can be organized into multiple tables.
This separation allows one to limit access to certain tables.
Works Cited
[1] http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/reldb/
