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Finally, even if youdefine many different indexes for a table, youdon??™t have to
understand them or manage the data they contain. Oracle includes a query optimizer
(described in Chapter 4) that chooses whether to use indexes, and the best way to
use those indexes, to access the data for any particular query.
The relational approach lent itself to the Structured Query Language (SQL). SQL
was initially defined over a period of years by IBM Research, but it was Oracle Corporation
that first introduced it to the market in 1979. SQL was noteworthy at the
time for being the only language needed for relational databases since you could use
SQL:
??? For queries (using a SELECT statement)
??? As a Data Manipulation Language or DML (using INSERT, UPDATE, and
DELETE statements)
??? As a Data Definition Language or DDL (using CREATE or DROP statements
when adding or deleting tables)
??? To set privileges for users or groups (using GRANT or REVOKE statements)
Today, SQL contains many extensions and follows ANSI/ISO standards that define
its basic syntax.


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