Can you explain what an alias means in SQL and in what cases it is used?

In SQL, an alias is a temporary name assigned to a table or column in a query for ease of reading and to shorten the notation. Aliases are used to simplify complex queries, especially when working with multiple tables or when there is a need to rename a column in the output.

Example of using an alias for a column:

SELECT first_name AS Name, last_name AS Surname FROM employees;

Example of using an alias for a table:

SELECT e.first_name, d.department_name
FROM employees AS e
JOIN departments AS d ON e.department_id = d.department_id;

Aliases are useful when you want to make a query more readable or when column/table names are too long or inconvenient for reuse.