SQL can be divided into two parts: The Data Manipulation Language
(DML) and the Data Definition Language (DDL).
The query and update commands form the DML part of SQL:
v SELECT -
extracts data from a database
v UPDATE -
updates data in a database
v DELETE -
deletes data from a database
v INSERT
INTO - inserts new data into a database
The DDL part of SQL permits database tables to be created or
deleted. It also defines indexes (keys), specifies links between tables, and
imposes constraints between tables.
The most important DDL statements in SQL
are:
Ø CREATE
DATABASE - creates a new database
Ø ALTER
DATABASE - modifies a database
Ø CREATE
TABLE - creates a new table
Ø ALTER TABLE -
modifies a table
Ø DROP
TABLE - deletes a table
Ø CREATE
INDEX - creates an index (search key)
Ø DROP
INDEX - deletes an index
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