Common Table Expression In SQL Server

Exploring the Power of Common Table Expressions (CTEs) in SQL: Syntax and Examples

Introduction

SQL CTE (Common Table Expression) is a powerful feature in SQL that allows you to define temporary named result sets that can be used within the context of a single SQL statement. CTEs are similar to subqueries, but they offer some key advantages, including better readability and performance.

CTEs can be used in a variety of scenarios, such as when you need to perform complex data transformations or when you need to reuse the same subquery multiple times within a single SQL statement. In this article, we’ll explore some interesting examples of how to use SQL CTEs to perform some common tasks.

Example 1: Recursive Queries

One of the most common use cases for CTEs is to perform recursive queries. Recursive queries are queries that involve self-referencing tables or hierarchies. Let’s say you have a table called “employees” that contains information about employees, including their names, titles, and managers. You can use a CTE to retrieve the hierarchy of all employees in the organization, starting from the CEO.

Here’s an example of how to use a CTE to retrieve the hierarchy of all employees: