Aliases
SQL aliases are used to give a table, or a column in a table, a temporary name.
Aliases are often used to make column names more readable.
An alias only exists for the duration of that query.
An alias is created with the AS keyword.
Example
SELECT customer_id AS id
FROM customers;
AS is Optional
Actually, you can skip the AS keyword and get the same result:
Example
SELECT customer_id id
FROM customers;
Concatenate Columns
The AS keyword is often used when two or more fields are concatenated into one.
To concatenate two fields use ||.
Example
SELECT product_name
|| unit AS product
FROM products;
Note: In the result of the example above we are missing a space between product_name and unit. To add a space when concatenating, use
|| ' ' ||.
Example
SELECT product_name || ' ' || unit AS product
FROM products;
Using Aliases With a Space Character
If you want your alias to contain one or more spaces, like "My Great Products", surround your alias with double quotes.
Example
SELECT product_name AS "My Great Products"
FROM products;