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Article : What is SQL?
by John L
SQL stands for Structured Query Language and is the
lingua franca in the database world.
SQL is a standard that is used by all database
vendors and programmers to define, extract and
access the information that is stored in databases.
SQL began life as an IBM creation but was
standardized by the American National Standards
Institute (ANSI) and the International Organization
for Standardization (ISO) as ANSI/ISO SQL in 1988.
Since then ANSI/ISO SQL standard continued to
evolve. The ANSI-SQL group has since published three
standards over the years:
1. SQL89 (SQL1)
2. SQL92 (SQL2)
3. SQL99 (SQL3)
SQL is a query language. It is English-like and easy
to use.
However, although there are more than 90 SQL
reserved words, most programmers seldom use more
than the following handful of commands - SELECT,
INSERT, UPDATE, DELETE, FROM, WHERE, HAVING,
BETWEEN, LIKE, OR, AND, NOT, IN, ORDER, GROUP and
BY. For example, if you had a database table named
"employees" and you wanted to retrieve all records
where the employee has the last name "goodman", you
would use the following SQL statement: SELECT * FROM
employees WHERE lastname = 'goodman'; There are many
different categories of SQL statements but the basic
ones which all programmers should be familiar with
are the SQL statements that:
1. Create tables and manipulate their definitions
2. Query the table data
3. Manipulate the table data SQL is predominantly
used by 2 types of users - programs and humans
(keying in the commands through a database client) -
to pass instructions to databases.
SQL commands can be keyed into a database client
like the MySQL Query Browser or the SQL Server
Enterprise Manager and executed to either return a
result or modify records in the database. SQL can
also be used in conjunction with programming
language or scripting language like Microsoft Visual
Basic or PHP to communicate with the database.
Although SQL is a world standard, it is unfortunate
that most database vendors have come up with
different dialects and variations. This is because
every database vendor wants to differentiate their
database products from the crowd. One good example
is Microsoft SQL Server's TRANSACT-SQL. TRANSACT-SQL
is a superset of SQL and is designed for use only
with Microsoft SQL Server.
Although it does make programming much easier for
software developers, it is not compliant with other
databases like Oracle or MySQL - making TRANSACT-SQL
programs non database-portable.
As such, although many of these features are
powerful and robust, it is good practice to exercise
caution and limit your SQL use to be compliant with
the ANSI/ISO SQL standards and ODBC-Compliant.
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