SQL Aliases

Aliases are temporary names you assign to columns or tables to make query results cleaner or easier to read.

They are especially useful in:

  • Renaming column headers in output
  • Using shorter table names (especially with JOINs)
  • Improving readability

🔹 Column Alias Syntax

SELECT column_name AS alias_name
FROM table_name;

You can also omit AS:

SELECT column_name alias_name
FROM table_name;

✅ Aliases with spaces must be in double quotes or square brackets.

📌 Example: Column Alias

SELECT
  first_name AS "First Name",
  salary AS income
FROM employees;

🔹 Table Alias Syntax

SELECT t.column1, t.column2
FROM table_name AS t;

Also works without AS:

SELECT t.column1, t.column2
FROM table_name t;

📌 Example: Table Alias in JOIN

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

✅ Makes long queries much cleaner.

🧠 Quick Recap

Key PointExplanation
Column AliasTemporarily rename output column headers
Table AliasShorten table names for cleaner syntax
AS OptionalAS keyword is optional, but improves clarity
Quotes NeededUse quotes for aliases with spaces or special chars

💡 Use aliases to write cleaner, clearer SQL – especially in joins and reports.