1. Column Alias

SELECT first_name AS fname, last_name AS lname
FROM employees;

This changes the column headers in the result to fname and lname.

2. Table Alias

SELECT e.first_name, e.department
FROM employees AS e
WHERE e.salary > 50000;

Shortens the table name to e for easier reference.

Best Practices

• Use aliases to shorten lengthy table names in complex joins.
• Make alias names descriptive to clarify the query context.

Key Takeaways

• AS improves readability by renaming columns or tables.
• Aliases can reduce typing in complex queries with multiple joins.