Introduction to SQL (Structured Query Language)
By Stephen Bucaro
IBM developed the relational database model, however it wasn't given much support
because at the time IBM had a leading position in the database market with it's
hierarchical Information Management System (IMS). In 1979 a small company named
Relational Software released a Relational Database Management System (RDBMS)
Oracle had such an impact on the market that IBM quickly developed its relational
database management system by creating a language initially named SEQUEL
(Structured English Query Language). However when ready to release the product,
IBM's legal department found a possible copyright issue with the name SEQUEL. So
they decided to drop the vowels and call the language SQL.
Most people think SQL stands for "Structured Query Language", however SQL does
not have the required characteristics to be a structured language. SQL was designed
to allow untrained users to access relational data using English-like queries. Although
there is a lot you can do with SQL statements alone, to create the functions of a
complete database application you must call SQL statements with a fully structured
language like C++, PHP, or Java.
A relational database is a collection of data items where the data and relations
between them are organized in tables. A table is a collection of rows which are called
records and each row in a table contains the same columns which are called fields.
If we had a table of books, we could use the following query to return a list of books
with a price greater than 100.00.
SELECT * FROM Book WHERE price > 100.00 ORDER BY title;
The asterisk (*) after SELECT indicates that all columns of the Book table should
be included in the results. The ORDER BY indicates the result should be sorted in
ascending order (alphabetically) by title. The query retrieves all rows from the Book
table in which the price column contains a value greater than 100.00.
Other companies desiring to compete in the database industry modeled their
languages after SQL, and in 1986 ANSI (American National Standards Institute)
released the SQL-86 standard. The standard was adapted internationally in 1987 as
the ISO (International Organization for Standardization) as ISO/IEC 9075.
The most popular SQL database today is Oracle 11g, which is powerful enterprise
grade database. Oracle also has a Oracle 11g Express Edition (Oracle Database XE)
which is an entry-level, small-footprint database based on the Oracle 11g. It's free
to develop, deploy, and distribute; fast to download; and simple to administer.
The second most popular SQL database is MySQL. It's a powerful enterprise grade
database that runs on the Windows and Linux operating systems. MySQL was a
free open-source database supported by a large user community. However in January
of 2010 Oracle purchased MySQL and is now suppressing development of the free
version and creating proprietary pay versions.
MariaDB is a community-developed version of the MySQL relational database
management system intended to remain free under the GNU GPL. The MariaDB
Foundation it is being led by the developers of the original MySQL, who created it due
to concerns over MySQL's acquisition by Oracle.
The third most popular SQL database is Microsoft's SQL Server. SQL Server is a
powerful enterprise grade database that runs on the Windows and Linux operating
systems. Microsoft also has SQL Server Express, which is a free lightweight version
for Web Sites and desktop applications.