SQL Aliases

SQL Aliases

Aliases are temporary names given to columns or tables in a query. They improve readability and make complex queries easier to write and understand.

Column Alias Syntax

SELECT column_name AS alias_name
FROM table_name;

Example: Column Alias

SELECT name AS customer_name,
       email AS contact_email
FROM customers;

Alias Without AS

The AS keyword is optional in many database systems.

SELECT name customer_name
FROM customers;

However, using AS improves clarity and is recommended.

Alias with Expressions

Aliases are especially useful when working with computed columns.

SELECT price * quantity AS total_price
FROM order_items;

Using Alias in ORDER BY

You can reference a column alias in ORDER BY.

SELECT price * quantity AS total_price
FROM order_items
ORDER BY total_price DESC;

Table Aliases

Table aliases are useful when joining multiple tables or when writing long table names.

SELECT c.name, o.order_date
FROM customers AS c
JOIN orders AS o
  ON c.id = o.customer_id;

Why Table Aliases Matter

• Shorter queries
• Clear distinction between columns from different tables
• Required when the same table is used multiple times (self join)

Common Mistakes

• Forgetting to use the alias consistently
• Using unclear alias names like a, b, c in complex queries
• Confusing column aliases with actual table column names

Next Step

Continue with SQL Joins to learn how to combine data from multiple tables.