Types of CTE in SQL Server

In SQL Server Common Table Expressions are mainly of two types.

1. Non Recursive CTE

Non Recursive Common Table Expression also known as simple CTE is mainly used to create a temporary result set for queries that are not much complex in nature and which involves iterative operations only. The Non Recursive CTE’s enhances the readability of the code by breaking down the complex queries into small chunks.

Syntax of Non Recursive CTE:

WITH cte_name (column1, column2, ...) AS
(
    -- CTE query definition
    SELECT column1, column2, ...
    FROM your_table
    WHERE condition
)

SELECT *
FROM cte_name;

2. Recursive CTE

Recursive Common Table Expression also known as hierarchical or iterative CTE is mainly used to create a temporary result set for queries that are complex in nature. These are very useful when we are executing our queries in the databases which consists of hierarchical data structures. These CTE’s refer to their own output until the query statisfies the required condition. To terminate the recursive query we use the WHERE condition.

You must follow some rules in order to define the recursive CTE.

Syntax of Recursive CTE:

WITH RecursiveCTE (column1, column2, ...) AS
(
    SELECT column1, column2, ...
    FROM your_table
    WHERE condition
    
    UNION ALL
    
    -- Recursive member
    SELECT column1, column2, ...
    FROM your_table
    WHERE condition
)

SELECT *
FROM RecursiveCTE;

SQL Server is a relational database management system (RDBMS) that is used to handle complex data and maintain it in of tabular manner. With the help of SQL Server, one can easily protect their data as it provides various security features.

In this article, we are going to explore SQL server‘s CTE also known as Common Table Expressions. They are like virtual temporary tables that are created during the query execution and deleted once the query is executed completely. We will learn about the SQL Server CTE in depth manner along with its types and some examples with the practical implementations and so on.