SQL Aliases Tutorial

Example Table

We will use the following table named employees for our examples:

CREATE TABLE employees (
    id INT PRIMARY KEY,
    first_name VARCHAR(50),
    last_name VARCHAR(50),
    department VARCHAR(50),
    salary DECIMAL(10, 2)
);

INSERT INTO employees (id, first_name, last_name, department, salary) VALUES
(1, 'John', 'Doe', 'Engineering', 75000.00),
(2, 'Jane', 'Smith', 'Marketing', 65000.00),
(3, 'Sam', 'Brown', 'Engineering', 80000.00),
(4, 'Sue', 'Johnson', 'HR', 60000.00),
(5, 'Mike', 'Davis', 'Marketing', 70000.00);

Using Column Aliases

Column aliases are used to give a column in a table a temporary name. This can make the column header in your result set more readable.

SELECT first_name AS 'First Name', last_name AS 'Last Name', salary AS 'Annual Salary' FROM employees;

Result:

Using Table Aliases

Table aliases are used to give a table a temporary name, often used to make queries easier to read and write, especially when dealing with multiple tables.

SELECT e.first_name, e.last_name, e.salary FROM employees AS e;

Result:

Using Aliases in Joins

Aliases are particularly useful in JOIN operations to distinguish columns from different tables.

CREATE TABLE departments (
    id INT PRIMARY KEY,
    name VARCHAR(50)
);

INSERT INTO departments (id, name) VALUES
(1, 'Engineering'),
(2, 'Marketing'),
(3, 'HR');

SELECT e.first_name, e.last_name, d.name AS 'Department'
FROM employees AS e
JOIN departments AS d ON e.department = d.name;

Result: