SQL Aliases (AS Keyword) – Complete Guide with Examples (2026-27)

✅ What is a SQL Alias?

✅ A SQL alias is a temporary name assigned to a column or table in a query using the AS keyword.

✅ Column alias — renames a column in the query output. SELECT Name AS EmployeeName

✅ Table alias — gives a short name to a table for use within the same query. FROM Employees AS e

✅ The alias only exists for the duration of the query — it does not change the actual column or table name in the database.

✅ The AS keyword is optional in most databases — but always include it for readability.

✅ Sample Employees Table – used in all examples below:-

✅ SQL Alias Syntax

Column Alias Syntax

SELECT column_name AS alias_name
FROM table_name;

Table Alias Syntax

SELECT alias.column_name
FROM table_name AS alias;

✅ AS:- Keyword that assigns the alias. Optional but strongly recommended for readability.

✅ alias_name:- The temporary name. No spaces allowed unless wrapped in quotes or brackets.

✅ Example 1 – Column Alias: Rename a Column in the Output

Rename the Name column to EmployeeName and Salary to MonthlySalary in the query output:

✅ SELECT Query:-

SELECT Name AS EmployeeName,
       Salary AS MonthlySalary
FROM Employees;

✅ Result Show:-

✅ Example 2 – Column Alias with Spaces

If the alias name needs to contain spaces, wrap it in square brackets (SQL Server), backticks (MySQL), or double quotes (PostgreSQL/standard SQL):

✅ SQL Server / MS Access:-

SELECT Name AS [Employee Name],
       Salary AS [Monthly Salary]
FROM Employees;

✅ MySQL:-

SELECT Name AS `Employee Name`,
       Salary AS `Monthly Salary`
FROM Employees;

✅ PostgreSQL / Standard SQL:-

SELECT Name AS "Employee Name",
       Salary AS "Monthly Salary"
FROM Employees;

✅ Result Show:-

✅ Example 3 – Multiple Column Aliases in One Query

Rename all selected columns with clear, readable aliases:

✅ SELECT Query:-

SELECT ID       AS EmployeeID,
       Name     AS EmployeeName,
       Department AS Dept,
       Salary   AS MonthlySalary,
       City     AS Location
FROM Employees
WHERE Department = 'IT';

✅ Result Show:-

✅ Example 4 – Alias on Aggregate Functions (Most Common Use)

Without an alias, aggregate function results have ugly headers like COUNT(*) or AVG(Salary). Aliases fix this:

✅ SELECT Query:-

SELECT
  COUNT(*)              AS TotalEmployees,
  MIN(Salary)           AS LowestSalary,
  MAX(Salary)           AS HighestSalary,
  ROUND(AVG(Salary), 2) AS AverageSalary,
  SUM(Salary)           AS TotalSalaryBill
FROM Employees;

✅ Result Show:-

✅ Example 5 – Alias in GROUP BY and ORDER BY

Use the alias in ORDER BY to sort by the aliased column. In most databases you can also reference aliases in GROUP BY:

✅ SELECT Query:-

SELECT Department,
       COUNT(*)              AS TotalEmployees,
       ROUND(AVG(Salary), 2) AS AvgSalary
FROM Employees
GROUP BY Department
ORDER BY TotalEmployees DESC, AvgSalary DESC;

✅ Result Show:-

✅ Example 6 – Table Alias (Shortening Long Table Names)

Table aliases shorten long table names for use throughout the query. Instead of writing Employees.Name repeatedly, write e.Name:

✅ SELECT Query:-

SELECT e.Name AS EmployeeName,
       e.Department,
       e.Salary AS MonthlySalary
FROM Employees AS e
WHERE e.Salary > 8000
ORDER BY e.Salary DESC;

✅ Result Show:-

✅ Example 7 – Table Alias in JOIN Queries

Table aliases are most valuable in JOIN queries — they make the query much shorter and prevent ambiguity when both tables have a column with the same name:

✅ Sample Departments Table:-

✅ SELECT Query – JOIN with table aliases:-

SELECT e.Name     AS EmployeeName,
       e.Salary   AS MonthlySalary,
       d.DeptName AS Department,
       d.Location AS DeptLocation
FROM Employees AS e
JOIN Departments AS d
  ON e.Department = d.DeptName
WHERE e.Salary > 8000;

✅ Result Show:-

✅ Example 8 – Alias with Concatenation (Computed Column)

Use an alias to name a computed or concatenated column — for example combining Name and City into one readable column:

✅ MySQL / PostgreSQL – Concatenation with alias:-

SELECT CONCAT(Name, ' - ', City) AS EmployeeLocation,
       Salary AS MonthlySalary
FROM Employees
ORDER BY Salary DESC;

✅ SQL Server – Concatenation with alias:-

SELECT Name + ' - ' + City AS EmployeeLocation,
       Salary AS MonthlySalary
FROM Employees
ORDER BY Salary DESC;

✅ Result Show:-

✅ Column Alias vs Table Alias – Quick Comparison

✅ Key Points to Remember

✅ AS assigns a temporary alias — the actual column/table name in the database never changes.

✅ Column alias renames the output header — use it on every aggregate function for clear reporting.

✅ Table alias shortens table references — especially useful in JOINs and subqueries.

✅ AS is optional but always include it — omitting AS makes code harder to read.

✅ Column aliases can be used in ORDER BY — but NOT in WHERE or HAVING in most databases.

✅ Use underscores, not spaces, in aliases — Employee_Name works in all databases without special quoting.

✅ Once a table alias is set, use it consistently — you cannot mix Employees.Name and e.Salary in the same query.

✅ Table aliases are mandatory in self-JOINs — you must alias both copies of the table to distinguish them.

✅ Always alias computed columns — expressions like CONCAT(Name, City) must have an alias to be readable.

✅ Common SQL Alias Mistakes to Avoid