Overview of Database Management System (DBMS) Part – 6

Database Operation Language

A database application delivers a Data Definition Language (DDL) to stipulate the database schema as well as a Data Manipulation Language (DML) to define database queries plus alteration In reality, the Data Definition Language (DDL) and Data Manipulation Language (DML) are not two (2) distinct languages; as a substitute they merely form portions of a single database language, like the commonly known Structured Query Language (SQL).

Data Definition Language (DDL)

The description of a database schema is done by means of a group of demarcations stated by means of a superior language known as a Data Definition Language (DDL). For an instance, the subsequent code in the Structured Query Language (SQL) describes the Customer table or relation:

Create Table Customer ( Customer_ID VarChar ( 10 ) , Customer_Name Char ( 30 ) , Customer_Address VarChar ( MAX ) , Customer_Phone VarChar ( 12 ) )

Implementation of the abovementioned Data Definition Language (DDL) code forms the Customer table or relation. Furthermore, it updates a different group of relations or tables known as the data dictionary or data directory.

A data dictionary or data directory has metadata – which is, information about information. The schema of a table or relation is an instance of metadata. A database system refers the data dictionary or data directory in advance of reading or else writing or altering the real information.

The description about the storing arrangement as well as right to use techniques castoff by means of the database application through a group of code in a different form of Data Definition Language (DDL) is known as a data storage and definition language. These codes describe the application particulars of the database schemas, which are generally concealed from the end users. The information values kept in the database should fulfill definite reliability constrictions. For an instance, let’s assume the outstanding balance of a saving account must not be less than $ 50. The Data Definition Language (DDL) offers services to agree with such type of constrictions. The database applications examine these constrictions every single time the database is reorganized.

Data Manipulation Language (DML)

Data manipulation is the recovery of data kept in the database, adding fresh data into the database, removal of existing data from the database as well as the alteration of data deposited in the database. A Data Manipulation Language (DML) is a language which permits end users the right of entry or else manipulates information as structured by means of the suitable information modeling. There are fundamentally two (2) categories:

· Procedural Data Manipulation Language (DML) needs an end user to stipulate what information is desirable as well as by what method to acquire that information.

· Declarative Data Manipulation Language (DML) is also mentioned as non – procedural Data Manipulation Language (DML). It necessitates an end user to state what information is desirable but devoid of stipulating by what method to acquire that information. Declarative Data Manipulation Language (DML) is generally stress-free to study as well as easy to practice than the procedural Data Manipulation Language (DML). But, as end users do not have to state by what method to acquire the information, the database application has to work out an effectual method of retrieving information. The Data Manipulation Language (DML) module of the Structured Query Language is non – procedural.

A query is a code demanding the retrieval of data. The part of a Data Manipulation Language (DML) which includes data rescue is known as a query language. Though in theory inappropriate, it is common use to practice the terms query language as well as data manipulation language (DML) synonymously.

The stages of generalization are applied not only to describe or organize the information, but also to manage the information. In the physical stage one should describe procedures which permit the effective access to information. In the advanced stages of generalization, one put emphasis on comfort of usage. The aim is to permit individuals to relate proficiently with the database application. The query processor module of the database application interprets Data Manipulation Language (DML) queries into arrangements of activities at the physical stage of the database application.

In the upcoming part we will be discussing the Data Dictionary or Data Directory and the Database Administrators (DBA) and Database End Users.