Many database management systems support some version of structured query language (SQL). In some DBMSs (i.e., ORACLE) SQL is the primary data manipulation interface. Consequently, SQL is a very important topic. The purpose of this document is to introduce you to the major SQL statements and to show you how they work. This document will concentrate primarily on ORACLE SQL; however, some attention also will be given to other versions of SQL. This is not a complete reference of SQL. If you are interested in a more detailed coverage I can suggest several good textbooks for outside reading.
SQL commands can be broken into the 3 following functional groups: .
Data Definition Language (DDL)
used to define the schema (structure) of the database
- CREATE TABLE
- ALTER TABLE
- CREATE INDEX
- DROP TABLE
- DROP INDEX
Data Manipulation Language (DML)
used to retrieve and update from the database
- SELECT
- INSERT
- UPDATE
- DELETE
Data Control Language (DCL)
used to manipulate the processing of data and erform other misc. functions
- COMMIT
- ROLLBACK