PostgreSQL Aliases

We can use SQL to rename a table or a column, and this new name is called an alias for the table or column.

Creating aliases enhances the readability of table names or column names.

In SQL, the AS keyword is used to create aliases.

Syntax

Table alias syntax:

SELECT column1, column2....
FROM table_name AS alias_name
WHERE [condition];

Column alias syntax:

SELECT column_name AS alias_name
FROM table_name
WHERE [condition];

Example

Create the COMPANY table (download COMPANY SQL file), with the following data:

tutorialprodb# select * from COMPANY;
 id | name  | age | address   | salary
----+-------+-----+-----------+--------
  1 | Paul  |  32 | California|  20000
  2 | Allen |  25 | Texas     |  15000
  3 | Teddy |  23 | Norway    |  20000
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
  6 | Kim   |  22 | South-Hall|  45000
  7 | James |  24 | Houston   |  10000
(7 rows)

Create the DEPARTMENT table (download DEPARTMENT SQL file), with the following data:

tutorialprodb=# SELECT * from DEPARTMENT;
 id | dept        | emp_id
----+-------------+--------
  1 | IT Billing  |      1
  2 | Engineering |      2
  3 | Finance     |      7
  4 | Engineering |      3
  5 | Finance     |      4
  6 | Engineering |      5
  7 | Finance     |      6
(7 rows)

Now, we will use C and D as aliases for the COMPANY and DEPARTMENT tables respectively:

tutorialprodb=# SELECT C.ID, C.NAME, C.AGE, D.DEPT FROM COMPANY AS C, DEPARTMENT AS D WHERE  C.ID = D.EMP_ID;

The result is as follows:

id | name  | age |  dept
----+-------+-----+------------
  1 | Paul  |  32 | IT Billing
  2 | Allen |  25 | Engineering
  7 | James |  24 | Finance
  3 | Teddy |  23 | Engineering
  4 | Mark  |  25 | Finance
  5 | David |  27 | Engineering
  6 | Kim   |  22 | Finance
(7 rows)

Next, we will use COMPANY_ID for the ID column and COMPANY_NAME for the NAME column to demonstrate column aliases:

tutorialprodb=# SELECT C.ID AS COMPANY_ID, C.NAME AS COMPANY_NAME, C.AGE, D.DEPT  FROM COMPANY AS C, DEPARTMENT AS D WHERE  C.ID = D.EMP_ID;

The result is as follows:

company_id | company_name | age | dept
------------+--------------+-----+------------
      1     | Paul         |  32 | IT Billing
      2     | Allen        |  25 | Engineering
(7 rows)

7 | James | 24 | Finance 3 | Teddy | 23 | Engineering 4 | Mark | 25 | Finance 5 | David | 27 | Engineering 6 | Kim | 22 | Finance (7 rows)