8. Data Manipulation Language

A Database Management System includes a 'Data Manipulation Language' or DML.

The DML provides the user with a set of commands to

• Insert records into the database
• Delete records
• Change or amend records
• Access / extract records by setting up a query

A very popular example of a DML is a language called SQL (Structured Query Language).

SQL statement consist of a main command such as SELECT / INSERT / UPDATE / DELETE which is followed by what is to be acted upon such as table / query and finally a condition section that limits the action in some way.

For example a simple command to extract the records from the employee table of user 'henry' looks like this

SELECT * FROM 'employee' WHERE user='henry'.

The action bit is the SELECT, the star means 'all'. The FROM clause defines the tables to be examined - in this case the employee table and the WHERE clause limits the records to those that match the criteria user = henry.

Data Manipulation Language (DML) is a fourth generation language (4GL). This is explained more fully in section 5.4.5 'Types of Language' mini-website.