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DQL Full Form

  • Difficulty Level : Medium
  • Last Updated : 16 Nov, 2020

Structured Query Language (SQL) is a non procedural language used for retrieving data from the queries. It was introduced by IBM as a part of R project. It was declared as a standard language by ANSI and ISO. 

It has subcategories: 

  • DDL or Data Definition Language has commands like create, rename, alter. 
  • DML or Data Manipulation Language has commands like update, insert, delete. 
  • DCL or Data Control Language has commands like grant and revoke. 
  • TCL or Transaction Control Language has commands like rollback, commit. 

Data Manipulation Language has a subcategory: 

Data Query Language (DQL) or Data Retrieval Language (DRL). Data Query Language has commands that retrieve the data from the query. It has a single command: select. 

Characteristics of DQL: 
It is used for retrieving data. A user can retrieve data according to his/her requirements using select command. 

If a user want to retrieve all the from the employee table, the query must be given as follows: 

select *
from employee;  

asterisk mark (*) indicates that all the rows is retrieved from the table. 

If a user want to know the average salary of the employees, the query must be given as follows: 

select avg(salary) 
from employee; 

This displays the average salary of the employees. 
Here asterisk mark isn’t needed as we need to retrieve only particular rows. 

If a user wants to know the name of the employee whose salary is less than 10, 000;the query is: 

select ename 
from employee 
where salary<=10, 000; 

A condition is placed to retrieve the data and a relational operator is used as well. 


  • select is a standard command used for almost every query.
  • It can also be written as SELECT as SQL is a case insensitive language.
  • It makes the data retrieving process more easier.
  • No coding needed.
  • This domain language can be used for communicating with the databases and receive answers to the complex questions in seconds.


  • Data Query Language has no disadvantages.
  • It is not possible to imagine Structured Query Language without the select command.
  • Interfacing an DQL database is more complex than adding a few lines of code.
  • The operating cost of some DQL versions makes it difficult for some programmers to access it.


  • Analytical Queries.
  • Retrieve Information from database.
  • Modify the index structures and database table.

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