Databases Reference
In-Depth Information
of keys and integrity constraints across related tables such as foreign keys. A row of any
table consists of columns of structured data, and the database as a whole contains only
structured data. The logical model of the data held in the database is based on tables and
relationships.
For example, for an
Employee
table we can define the columns as
Employee_ID,
First_Name, Initial, Last_Name, Address_Line_1, Address_Line_2, City, State, Zip_Code,
Home_Tel_No, Cell_Tel_No
. In the database schema, we further define the data types for
each one of these columns:
integer, char, varchar
, etc. These column names feature in
the SQL queries as data of interest for the user. We call this structured data because the
data held in the database is represented in a tabular fashion and is known in advance and
recorded in a schema.
The Non-Relational Database:
Since RDBMS is confined to representing data as
related tables made up of rows and columns, it does not easily accommodate data that
have nested or hierarchical structures such as a bill of materials or a complex document.
Non-relational databases cater to a wider variety of data structures (older mainframe
data structures, object and object-relational data structures, document and XML data
structures, graph data structures, etc.) than just tables. What we have defined here is an
“everything else bucket” that includes all databases that are not purely relational.
OldSQL, NewSQL, and the Emerging NoSQL
The relational database was driven by the idea of database standardization around a
generally applicable structure of data to store the data, and a universally acceptable
interface like SQL to query the data. We will refer to the traditional RDBMS systems as
OldSQL databases. These technologies have proven to be excellent for most transactional
data and also for querying and analyzing broad collections of corporate data. These
databases are characterized by the use of SQL as the primary means of data access,
although they may have other data access features.
There is also a relatively new category of relational databases that although they
adhere to the traditional RDBMS philosophy they are designed differently, extending
the relational model. A key offering of these databases is new architectures to improve
performance, scalability, and most commonly scale-out. They include such products as
Infobright, SAP Sybase IQ, Greenplum, ParAccel, SAND Technologies, Teradata, Vertica,
Vectorwise,
and others. We categorize these as NewSQL databases, since they employ SQL
as their primary means of access and fundamentally deal with structured data only.
There is also an emerging set of databases specifically designed to provide non-SQL
modes of data access. These are commonly categorized as NoSQL databases for their
definition of “not only SQL” or “noSQL at all.” These NoSQL databases exhibit a wide
range of characteristics and design philosophies.
Figure
4-2
illustrates the area of applicability of OldSQL, NewSQL, and NoSQL.
