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An Introduction to CTEs in SQL

Explore how Common Table Expression (CTE) can help optimize SQL performance and readability

Eugenia Anello
TDS Archive
6 min readDec 4, 2024

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Photo by SpaceX on Unsplash

In the past few months, I have learned the importance of writing clean, readable, and efficient SQL queries. They are essential for integrating information from different tables.

However, writing complex queries from scratch can be time-consuming, especially when you frequently use them for analyzing your data. To address this need, SQL offers a powerful construct, known as Common Table Expression.

In this article, I am going to explain what a Common Table Expression is, why it’s useful, and demonstrate its application through examples. Let’s get started!

Table of contents:

  • What is a Common Table Expression?
  • Setting up DBeaver and Database
  • Three simple examples of CTEs

What is a Common Table Expression?

A Common Table Expression (CTE) is a temporary result set that simplifies complex queries, making them more readable and maintainable. It works by breaking a complex query into smaller, more manageable pieces — essentially building on sequential, modular subqueries. It doesn’t just limit on managing complicated queries. It can also be…

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Eugenia Anello
Eugenia Anello

Written by Eugenia Anello

Data Scientist | Top 1500 Writer on Medium | Love to share Data Science articles| https://www.linkedin.com/in/eugenia-anello

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