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Introduction to PostgreSQL and PostgreSQL CTE, Upsert

This blog will discuss PostgreSQL and the uniqueness of PostgreSQL as compared to other open-source SQL software. Let us explore PostgreSQL Common Table Expressions (CTE), PostgreSQL Upsert (Update+Insert), and much more.

Introduction to PostgreSQL

PostgreSQL is a relational database management system that is sophisticated, enterprise-class, and open-source. PostgreSQL supports both relational and non-relational data querying. It is a robust database that the open-source community has developed for more than two decades.

Many online apps, mobile, and analytics applications use PostgreSQL as their primary database.

Top features of PostgreSQL

Many advanced features are available in PostgreSQL that are not available in other enterprise-class database management systems, such as:

Uniqueness of PostgreSQL

PostgreSQL is an object-relational database. It offers an advantage over MySQL, MariaDB, and Firebird, all open-source SQL databases. It supports many data types as described below:

PostgreSQL CTE

The CTE (Common Table Expression) is a temporary result set in PostgreSQL that the user can reference within another SQL operation such as SELECT, INSERT, UPDATE, or DELETE. CTEs are transitory because they exist only while the query is being executed. In PostgreSQL, CTEs are commonly used to simplify complex joins and subqueries.


The CTE’s name comes first, followed by an optional column list.

Second, specify a query that returns a result set inside the WITH clause’s body. If you do not mention the column list following the CTE name, the CTE query definition’s select list will be used as the CTE’s column list.

Third, treat the CTE like a table or view in the SELECT, INSERT, UPDATE, or DELETE statement.


Executing multiple queries using CTE

In this above query, we insert data into different tables in a single query without using any subqueries, breaking complex things into simpler ones.


The phrase upsert is also used as a merge in relational databases. If a row already exists in the table, PostgreSQL will update it; otherwise, it will insert the new row. Hence the action is known as upsert (update or insert).


One of the following actions could be taken:

DO NOTHING — If the row already exists in the table, do nothing.

WHERE condition – change some fields in the table. DO UPDATE SET column 1 = value 1


Now, insert data into it:


Let us check if doctor1 is present then we make him inactive, if he is not there in the table then we will insert a new record and set him too inactive.


In the above query, as id=1 already exists, only the update query worked, or else the insert query has worked. The column name we give in on conflict should be either unique or a primary key constraint.


Today we have gone through the Postgre SQL features and its unique characteristics which made Postgre SQL more popular among other open-source SQL software. We have used temporary tables i.e CTEs, which make our query more optimized.

About CloudThat

CloudThat is the official AWS (Amazon Web Services) Advanced Consulting Partner, Microsoft Gold Partner, Google Cloud Partner, and Training Partner helping people develop knowledge of the cloud and help their businesses aim for higher goals using best-in-industry cloud computing practices and expertise. We are on a mission to build a robust cloud computing ecosystem by disseminating knowledge on technological intricacies within the cloud space. Explore our consulting here.

If you have any queries regarding PostgreSQL and PostgreSQL CTE, Upsert, or any other service, drop a line below the comments section. I will get back to you at the earliest.


  1. What is PostgreSQL, and what does it cost?

PostgreSQL is an object-relational database system with the functionality of conventional proprietary database systems. The entire source code for PostgreSQL is available for everyone, and it is free.

  1. Where can I get PostgreSQL?

You can obtain the source code from

  1. Can we execute a CTE without a statement in the end?

No, You have to give a statement in the end to execute a CTE query.

WRITTEN BY Imraan Pattan

Imraan is a Software Developer working with CloudThat Technologies. He has worked on Python Projects using the Flask framework. He is interested in participating in competitive programming challenges and Hackathons. He loves programming and likes to explore different functionalities for creating backend applications.



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