A guide to SQL Aliases

A guide to SQL Aliases
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Using AS to assign meaningful or simpler names

You can use AS to assign a name to a column of data you are selecting or that has been calculated.

SELECT user_only_num1 AS AgeOfServer, (user_only_num1 - warranty_period) AS NonWarrantyPeriod FROM server_table

This results in output as below.

+-------------+------------------------+
| AgeOfServer | NonWarrantyPeriod      | 
+-------------+------------------------+
|         36  |                     24 |
|         24  |                     12 | 
|         61  |                     49 |
|         12  |                      0 | 
|          6  |                     -6 |
|          0  |                    -12 | 
|         36  |                     24 |
|         36  |                     24 | 
|         24  |                     12 | 
+-------------+------------------------+

You can also use AS to assign a name to a table to make it easier to reference in joins.

SELECT ord.product, ord.ord_number, ord.price, cust.cust_name, cust.cust_number FROM customer_table AS cust

JOIN order_table AS ord ON cust.cust_number = ord.cust_number

This results in output as below.

+-------------+------------+-----------+-----------------+--------------+
| product     | ord_number | price     | cust_name       | cust_number  |
+-------------+------------+-----------+-----------------+--------------+
|     RAM     |   12345    |       124 | John Smith      |  20          |
|     CPU     |   12346    |       212 | Mia X           |  22          |
|     USB     |   12347    |        49 | Elise Beth      |  21          |
|     Cable   |   12348    |         0 | Paul Fort       |  19          |
|     Mouse   |   12349    |        66 | Nats Back       |  15          |
|     Laptop  |   12350    |       612 | Mel S           |  36          |
|     Keyboard|   12351    |        24 | George Z        |  95          |
|     Keyboard|   12352    |        24 | Ally B          |  55          |
|     Air     |   12353    |        12 | Maria Trust     |  11          |
+-------------+------------+-----------+-----------------+--------------+