Overview of the SQL Query Language

IBM developed the original version of SQL, originally called Sequel, as part of the
System R project in the early 1970s. The Sequel language has evolved since then,
and its name has changed to SQL (Structured Query Language). Many products
now support the SQL language. SQL has clearly established itself as the standard
relational database language.

In 1986, the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) published an SQL standard, called
SQL-86. ANSI published an extended standard for SQL, SQL-89, in 1989. The next version of the standard was SQL-92 standard, followed by SQL:1999, SQL:2003, SQL:2006, and most recently SQL:2008. The bibliographic notes provide references to these standards.

The SQL language has several parts:

• Data-definition language (DDL): The SQL DDL provides commands for defin?ing relation schemas, deleting relations, and modifying relation schemas.

• Data-manipulation language (DML): The SQL DML provides the ability to
query information from the database and to insert tuples into, delete tuples
from, and modify tuples in the database.

• Integrity: The SQL DDL includes commands for specifying integrity con?straints that the data stored in the database must satisfy. Updates that violate
integrity constraints are disallowed.

• View definition: The SQL DDL includes commands for defining views.

• Transaction control: SQL includes commands for specifying the beginning
and ending of transactions.

• Embedded SQL and dynamic SQL: Embedded and dynamic SQL define how
SQL statements can be embedded within general-purpose programming languages, such as C, C++, and Java.

• Authorization: The SQL DDL includes commands for specifying access rights
to relations and views.

Frequently Asked Questions