PostgreSQL Alias

We can use SQL to rename a table or a field, and this name is called the alias of that table or field.

Creating aliases is to make table names or column names more readable.

In SQL, useASto create aliases.

Syntax

Syntax for table aliases:

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

Syntax for column aliases:

SELECT column_name AS alias_name
FROM table_name
WHERE [condition];

Examples

Create the COMPANY table (Download COMPANY SQL file), with the data content as follows:

exampledb# 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 COMPANY SQL file), with the data content as follows:

exampledb=# 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)

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

exampledb=# 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 use COMPANY_ID to represent the ID column and COMPANY_NAME to represent the NAME column to demonstrate the use of column aliases:

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