SQL Language

SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in a relational database.

SQL is the standard language for Relational Database System. All the Relational Database Management Systems (RDMS) like MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their standard database language.
SQL is widely popular because it offers the following advantages:

• Allows users to access data in the relational database management systems.

• Allows users to describe the data.

• Allows users to define the data in a database and manipulate that data.

• Allows to embed within other languages using SQL modules, libraries & pre-compilers.

• Allows users to create and drop databases and tables.

• Allows users to create view, stored procedure, functions in a database.

• Allows users to set permissions on tables, procedures and views.

When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task.
There are various components included in this process.
These components are:

• Query Dispatcher
• Optimization Engines
• Classic Query Engine
• SQL Query Engine, etc.

A classic query engine handles all the non-SQL queries, but a SQL query engine won't handle logical files.
The standard SQL commands to interact with relational databases are CREATE, SELECT, INSERT, UPDATE, DELETE and DROP. These commands can be classified into the following groups based on their nature:br>

DDL - Data Definition Language

Command	Description
CREATE	Creates a new table, a view of a table, or other object in the database.
ALTER	Modifies an existing database object, such as a table.
DROP	Deletes an entire table, a view of a table or other objects in the database.

DML - Data Manipulation Language

Command	Description
SELECT	Retrieves certain records from one or more tables.
INSERT	Creates a record.
UPDATE	Modifies records.
DELETE	Deletes records.

SQL-Syntax

SQL is followed by a unique set of rules and guidelines called Syntax. This tutorial gives you a quick start with SQL by listing all the basic SQL Syntax. All the SQL statements start with any of the keywords like SELECT, INSERT, UPDATE, DELETE, ALTER, DROP, CREATE, USE, SHOW and all the statements end with a semicolon (;). The most important point to be noted here is that SQL is case insensitive, which means SELECT and select have same meaning in SQL statements.

All the examples given in this tutorial have been tested with a Clomosy server.