SQL is a query language designed for
organizing, managing, developing and querying large relational databases over
computer networks. SQL is a common language in the Information Science (IS) and
Information Management industry. The language has been standardized by the
American National Standards Institute (ANSI) and the International Standards
Organization (ISO), meaning that there are specific features that must be
present in any version of SQL produced by a software company in order for that
version to be officially called SQL. Many software vendors add more advanced
features to their version of SQL in an effort to improve the language and
attract customers, but it must retain the original standards established by
ANSI and ISO.
SQL is not a true computer language. It
cannot be used to create stand-alone computer applications or operating
systems. SQL is often referred to as a sub-language, since it can be used
within other languages or applications. Most importantly, the purpose of the
SQL language is specific to working with relational databases.
The syntax of the SQL language is built on
a system of sending SQL statements to the SQL database server. Each statement
is a request to perform a database operation, such as creating a database file,
adding tables and fields to a database, adding records to tables, or retrieving
data from databases. The SQL server analyzes the SQL statement and performs the
required operation. For example, if the statement is a request for data, the
server gathers the data and returns it to the client workstation for the user
to view.
An SQL query is an SQL statement designed
specifically to request data from one or more SQL databases. Some SQL
applications require that you type in an SQL query directly using a text
editor, while others provide graphical user interfaces that lead you through
the process of querying an SQL database. In the latter case, the application
must create an SQL statement based on the information you provide. This
statement is the actual SQL query, and it is the SQL query that is used to
request the data.
Crystal Reports falls into both categories of SQL-compliant
applications.