Data Definition

Data Definition
The SQL Data Definition Language (DDL) allows database objects such as schemas,
domains, tables, views, and indexes to be created and destroyed. In this section, we briefly
examine how to create and destroy schemas, tables, and indexes. We discuss how to create
and destroy views in the next section. The ISO standard also allows the creation of
character sets, collations, and translations. However, we will not consider these database
objects in this book. The interested reader is referred to Cannan and Otten (1993).
The main SQL data definition language statements are:
CREATE SCHEMA DROP SCHEMA
CREATE DOMAIN ALTER DOMAIN DROP DOMAIN
CREATE TABLE ALTER TABLE DROP TABLE
CREATE VIEW DROP VIEW
These statements are used to create, change, and destroy the structures that make up the
conceptual schema. Although not covered by the SQL standard, the following two statements
are provided by many DBMSs:
CREATE INDEX DROP INDEX
Additional commands are available to the DBA to specify the physical details of data storage;
however, we do not discuss them here as these commands are system specific.