SQL Aliases

What are Aliases?

Aliases are temporary names given to columns or tables in a query.

They improve readability and simplify queries.

Column Aliases

SELECT name AS employee_name
FROM employees;

Without AS

SELECT name employee_name
FROM employees;

Aliases in Calculations

SELECT salary * 12 AS yearly_salary
FROM employees;

Table Aliases

SELECT e.name
FROM employees e;

Aliases in Joins

SELECT e.name, d.department_name
FROM employees e
JOIN departments d
ON e.department_id = d.id;

Aliases with Aggregate Functions

SELECT department,
       AVG(salary) AS avg_salary
FROM employees
GROUP BY department;

Full Example

SELECT e.name AS employee_name,
       e.salary * 12 AS yearly_salary
FROM employees e;

Why Aliases are Important

• Improve readability
• Simplify queries
• Required for joins
• Clarify output

Common Mistakes

• Forgetting aliases in joins
• Using spaces without proper formatting
• Confusing alias with actual column name

Practice

Rename a column and use a table alias.

SELECT column_name AS new_name
FROM table_name t;

Need Help?

Ask the AI if you need help understanding or want to dive deeper in any topic