SQL Alias Syntax
You can rename a table or a column temporarily by giving another name known as alias.
The use of table aliases means to rename a table in a particular SQL statement. The renaming is a temporary change and the actual table name does not change in the database.
The column aliases are used to rename a table's columns for the purpose of a particular SQL query.
Syntax:
The basic syntax of table alias is as follows:
SELECT column1, column2....
FROM table_name AS alias_name
WHERE [condition];
The basic syntax of column alias is as follows:
SELECT column_name AS alias_name
FROM table_name
WHERE [condition];
Example:
Consider the following two tables, (a) CUSTOMERS table is as follows:
+----+----------+-----+-----------+----------+
| ID | NAME | AGE | ADDRESS | SALARY |
+----+----------+-----+-----------+----------+
| 1 | Ramakrishna | 32 | Ahmedabad | 2000.00 |
| 2 | Mdhu sudhan rao | 25 | Delhi | 1500.00 |
| 3 | Sai | 23 | Kota | 2000.00 |
| 4 | Kishor | 25 | Mumbai | 6500.00 |
| 5 | Ranjith | 27 | Bhopal | 8500.00 |
| 6 | Abhi | 22 | MP | 4500.00 |
| 7 | Kumar | 24 | Indore | 10000.00 |
+----+----------+-----+-----------+----------+
(b) Another table is ORDERS as follows:
CHAPTER 27
29
+-----+---------------------+-------------+--------+
|OID | DATE | CUSTOMER_ID | AMOUNT |
+-----+---------------------+-------------+--------+
| 102 | 2009-10-08 00:00:00 | 3 | 3000 |
| 100 | 2009-10-08 00:00:00 | 3 | 1500 |
| 101 | 2009-11-20 00:00:00 | 2 | 1560 |
| 103 | 2008-05-20 00:00:00 | 4 | 2060 |
+-----+---------------------+-------------+--------+
Now, following is the usage of table alias:
SQL> SELECT C.ID, C.NAME, C.AGE, O.AMOUNT
FROM CUSTOMERS AS C, ORDERS AS O
WHERE C.ID = O.CUSTOMER_ID;
This would produce the following result:
+----+----------+-----+--------+
| ID | NAME | AGE | AMOUNT |
+----+----------+-----+--------+
| 3 | Sai | 23 | 3000 |
| 3 | Sai | 23 | 1500 |
| 2 | Mdhu sudhan rao | 25 | 1560 |
| 4 | Kishor | 25 | 2060 |
+----+----------+-----+--------+
Following is the usage of column alias:
SQL> SELECT ID AS CUSTOMER_ID, NAME AS CUSTOMER_NAME
FROM CUSTOMERS
WHERE SALARY IS NOT NULL;
This would produce the following result:
+-------------+---------------+
| CUSTOMER_ID | CUSTOMER_NAME |
+-------------+---------------+
| 1 | Ramakrishna |
| 2 | Mdhu sudhan rao |
| 3 | Sai |
| 4 | Kishor |
| 5 | Ranjith |
| 6 | Abhi |
| 7 | Kumar |
+-------------+---------------+
