Introduction to PostgreSQL (Coding Style) Part-5

This blog aims to assist you in understanding the concepts of PostgreSQL with complete coding as query language.

PostgreSQL SQL commands

Note: Make sure you have Postgres installed on your system to proceed to this tutorial.

PostgreSQL - ALIAS Syntax

• In PostgreSQL, aliases can be used to temporarily rename tables or columns in queries.

• Table aliases allow you to refer to a table by a different name within a specific query, but the actual table name remains unchanged in the database.

• Column aliases are used to rename specific columns in query results, providing more meaningful or concise names for presentation without altering the underlying data.

Syntax Of Table Alias:

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

Syntax Of Column Alias:

SELECT column_name AS alias_name
FROM table_name
WHERE [condition];

Example:

Consider the following two tables, (1) COMPANY table is as follows −

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

(2) DEPARTMENT as follows −

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

TABLE ALIAS

Note: Usage of TABLE ALIAS where we use C and D as aliases for COMPANY and DEPARTMENT tables, respectively −

Query:

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

Result:

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

Column ALIAS

Note: The usage of COLUMN ALIAS where COMPANY_ID is an alias of ID column and COMPANY_NAME is an alias of name column −

Query:

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;

Result:

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

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I hope this blog has helped you understand the concepts of PostgreSQL with complete coding as a query language.

Check out a summary of Part-6.