SQL SELECT AS Alias

SELECT last_name AS name
FROM Customers;

SQL AS Alias Syntax

The syntax of the SQL AS command is:

SELECT column_1 AS alias_1, 
    column_2 AS alias_2, 
…... column_n AS alias_n
FROM table_name;

Here,

• column_1, column_2,...column_n are the table columns
• alias_1, alias_2,...alias_n are the aliases of the table columns

For example,

SELECT first_name AS name
FROM Customers;

Here, the SQL command selects the first_name column of Customers. However, the column name will change to name in the result set.

SQL AS With More Than One Column

We can also use aliases with more than one column.

For example,

SELECT customer_id AS cid, first_name AS name
FROM Customers;

Here, the SQL command selects customer_id as cid and first_name as name.

SQL AS With Expression

We can combine data from multiple columns and represent it in a single column using the CONCAT() function. For example,

SELECT CONTACT(first_name, ' ', last_name) AS full_name
FROM Customers;

Here, the SQL command selects first_name and last_name. And, the name of the column will be full_name in the result set.

However, our online compiler does not support the CONCAT() function since it uses the SQLite library. Instead, you need to use the concatenation operator || to perform this task.

For example, here's an equivalent code that will run in our compiler.

-- concatenate first_name, empty space, and last_name into a single column named full_name in the result set

SELECT first_name || ' ' || last_name AS full_name
FROM Customers;

Here, the SQL command will concatenate the first_name and last_name columns in the result set as full_name.

Notice that we have also concatenated an empty space ' ' between first_name and last_name. This ensures that the data from these columns are separated by a space in the result set.

-- AS with functions
SELECT COUNT(*) AS total_customers
FROM Customers;

-- AS table alias
SELECT cu.first_name, cu.last_name
FROM Customers AS cu;

SELECT C.customer_id AS cid, C.first_name AS name, O.amount
FROM Customers AS C
JOIN Orders AS O
ON C.customer_id = O.customer_id;