What are database languages? Describe DML (DBMS)



Database Language: As whatever we want to be manipulated by computer has to be written using specific language, database is not beyond them. To write or create database management system we use database languages. They are of two types; Data Definition Language (DDL) and Data Manipulation Language (DML). DDL is used to design a database and DML is used express database’s queries and updates.



DML (Data Manipulation Language): A Data Manipulation Language is a database language which enables users to access and modify stored data in a database. The types of access are as follows,
  1. Retrieval of information stored in the database.
  2. Insertion of new information into the database.
  3. Deletion of information stored in the database.
  4. Modification of information stored in the database.


There are basically two types,
  1. Procedural DMLs: Procedural DMLs requires a user to specify what data are needed and how to get those data.
  2. Declarative DMLs: Declarative DML’s requires a user only to specify what data are needed. 

In the case of retrieval of information some statements are used which are called queries. The portion of DML that contains information retrieval statement is called query language.


Explanation with Example: Supposing that we are having the following table initially,
customer_id
customer_area
customer_order
0005
Uposahor_3
5
0006
Uposahor_2
10
0007
Uposahor_3
9
0008
Uposahor_3
8
Table: customers

Here, we have 3 attributes customer_id, customer_area, customer_order. Let that we want a list of those customer_id who are from Uposahor_3 area. To do this manipulation with the above table we are using SQL statements as follows,

                                                select customers.customer_id
from customers
where customers.customer_area = ‘Uposahor_3’

In the first statement it is defining the column that we need, in the next line it is defining the table and in the last it is giving the condition that each retrieved customer_id will have a value Uposahor_3 for the customer_area attribute. So the output will be as follows,

customer_id
005
007
008

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