SQL Aliases

Aliases give a column or table a temporary, friendlier name for the duration of the query.

Column aliases

SELECT name      AS customer,
       email     AS contact,
       price * quantity AS line_total
FROM line_items;

The AS keyword is optional but makes intent clearer. In SQL Server you can also write customer = name.

Table aliases

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

Table aliases are mandatory once a column name exists in more than one joined table.

Aliases with spaces or keywords

SELECT total AS "Total Revenue"
FROM orders;

Use double quotes (ANSI), backticks (MySQL), or square brackets (SQL Server) to wrap aliases that contain spaces, punctuation, or reserved words.

Where aliases work — and don't

Example

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

Exercise

Test yourself