What is SQL? 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.
Courtesty of SQLPrimer.com. For more
information, please contact the Webmaster of
SQLPrimer.com - http://www.sqlprimer.com.
About the author:
John L is the Webmaster of SQLPrimer.com -
http://www.sqlprimer.com.
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