Overview of SQL |
Structured Query Language (SQL) is a database access, nonprocedural language. Users issue SQL statements or commands to perform various tasks, such as retrieving data, and the SQL language compiler automatically handles how to navigate the database and perform the desired task. All database operations are performed using SQL.
This topic includes the following topics:
With SQL statements you can perform the following:
Query, insert, update, and delete data in tables
Format, perform calculations on, store, and print from query results
Examine table and object definitions
Develop and run batch scripts
Perform database administration
All operations performed on the information in an Oracle database are run using SQL statements. A statement consists partially of SQL reserved words, which have special meaning in SQL and cannot be used for any other purpose. For example, SELECT and UPDATE are reserved words and cannot be used as table names.
A SQL statement is an instruction. The statement must be the equivalent of a complete SQL sentence, as in:
SELECT last_name, department_id FROM employees;
Oracle SQL statements are divided into several categories:
Data Manipulation Language (DML) Statements
These statements query, insert, update, delete data in tables.
Transaction Control Statements
These statements commit or rollback the processing of transactions. A group of changes that you make is referred to as a transaction.
Data Definition Language (DDL) Statements
These create, alter, and drop database objects.