Data Query Language - DQL

DQL stands for Data Query Language, and it's a subset of SQL (Structured Query Language). It is used specifically to query data from a database without modifying it.

Key Characteristics of DQL:

Read-only: DQL is used to retrieve data, not to insert, update, or delete it.
The primary command used is:

SELECT

Example:

SELECT name, birthdate FROM customers WHERE city = 'Berlin';

This command retrieves the names and birthdates of all customers living in Berlin — without changing any data.

DQL vs Other SQL Sub-languages:

Sub-language	Meaning	Main Purpose
DQL	Data Query Language	Reading data
DML	Data Manipulation Language	Inserting, updating, deleting data (`INSERT`, `UPDATE`, `DELETE`)
DDL	Data Definition Language	Defining database structure (`CREATE`, `ALTER`, `DROP`)
DCL	Data Control Language	Managing access rights (`GRANT`, `REVOKE`)
TCL	Transaction Control Language	Handling transactions (`COMMIT`, `ROLLBACK`)