AS

SQL AS Keyword

The AS keyword in SQL is used to rename a column or a table with an alias. An alias is a temporary name that only exists during the execution of the query. Aliases are useful for making result sets easier to read or for simplifying complex queries.

SQL AS Syntax

For columns:

SELECT column_name AS alias_name
FROM table_name;

SELECT column_name AS alias_name

FROM table_name;

For tables:

SELECT column1, column2
FROM table_name AS alias_name;

SELECT column1, column2

FROM table_name AS alias_name;

SQL AS for Columns

The following SQL statement creates two aliases, one for the first_name column and one for the last_name column from the Patients table:

SELECT first_name AS First, last_name AS Last
FROM Patients;

SELECT first_name AS First, last_name AS Last

FROM Patients;

The following SQL statement creates two aliases. Notice that it uses double quotes since the alias contains a space:

SELECT first_name AS "First Name", last_name AS "Last Name"
FROM Patients;

SELECT first_name AS "First Name", last_name AS "Last Name"

FROM Patients;

The following SQL statement creates an alias named Details that combines three columns (first_name, last_name, and gender):

SELECT first_name || ' ' || last_name || ' - ' || gender AS Details
FROM Patients;

SELECT first_name || ' ' || last_name || ' - ' || gender AS Details

FROM Patients;

Note: In SQLite (used in our playground), || is used to concatenate text values.

SQL AS for Tables

The following SQL statement selects the appointment_date and first_name using aliases for both the Appointments and Patients tables:

SELECT a.appointment_date, p.first_name
FROM Appointments AS a, Patients AS p
WHERE a.patient_id = p.patient_id;

SELECT a.appointment_date, p.first_name

FROM Appointments AS a, Patients AS p

WHERE a.patient_id = p.patient_id;

SQL AS Labs