Structured Query Language (SQL)

Structured Query Language (SQL)

  Most large-scale databases use the Structured Query Language (SQL) to facilitate user and administrator interactions. This language offers a flexible interface for databases of all shapes and sizes. 

The first important point to make is that [em]all[/em] database transactions are made in SQL, whether you realize it or not. Nowadays, there are a large number of graphical user interfaces (GUIs) that simplify database administration tasks. If you're a SQL Server user, you may be familiar with tools like Enterprise Manager.

MySQL users may use any of a number of front ends. There are also quite a few third-party applications that interact with different databases (in fact, many of these can work with multiple database platforms simultaneously.) Did you ever wonder how these applications work? That’s right! They use SQL! The front-end translates your mouse clicks and text entries into SQL and then “speaks” to the database in the universal language of SQL.  

Flavors of SQL

SQL comes in many flavors. Oracle databases utilize their proprietary PL/SQL. Microsoft SQL Server makes use of Transact-SQL. However, all of these variations are based upon the industry standard ANSI SQL.

DDL and DML

SQL commands can be divided into two main sublanguages. The Data Definition Language (DDL) contains the commands used to create and destroy databases and database objects. After the database structure is defined with DDL, database administrators and users can use the Data Manipulation Language to insert, retrieve and modify the data contained within it.

DDL Definition: The Data Definition Language (DDL) is one of two major components of the Structured Query Language (SQL). It is used to alter the structure of tables within a relational databases. Some of the major commands comprising DML are CREATE TABLE, DROP TABLE and CREATE INDEX.

DML Definition: The Data Manipulation Language (DML) is one of two major components of the Structured Query Language (SQL). It is used to insert, retrieve and modify data stored within a relational databases. The major commands comprising DML are SELECT, INSERT, DELETE and UPDATE.