Converting a Scalar UDF to an Inline TVF in SQL Server скачать в хорошем качестве

Converting a Scalar UDF to an Inline TVF in SQL Server

Learn how to convert a scalar User-Defined Function into an Inline Table-Valued Function using CTE in SQL Server, while eliminating loops for better performance. --- This video is based on the question https://stackoverflow.com/q/74452565/ asked by the user 'Sam' ( https://stackoverflow.com/u/10362066/ ) and on the answer https://stackoverflow.com/a/74452836/ provided by the user 'John Cappelletti' ( https://stackoverflow.com/u/1570000/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Rewrite this Scalar UDF as a Inline TVF Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Converting a Scalar UDF to an Inline TVF in SQL Server Introduction If you’re working with SQL Server, you've likely encountered the need for creating User-Defined Functions (UDFs). While scalar UDFs serve their purpose, they can often hinder performance due to repeated calculations and loops. This blog will guide you through converting a Scalar UDF into a more efficient Inline Table-Valued Function (TVF) through the use of Common Table Expressions (CTEs). We’ll address a specific scenario: calculating business days from a given date. The Problem: Starting with a Scalar UDF Consider the following scalar UDF, which adds a specified number of business days to a given date. The original function loops through, increasing the date while skipping weekends. Here’s the function for reference: [[See Video to Reveal this Text or Code Snippet]] While this function does the job, it may not be efficient, especially as the numbers increase. You may also have noticed that its performance could degrade over larger datasets. The Solution: Converting to an Inline TVF Instead of using a loop, we can utilize an Inline TVF with a derived tally table to generate the required business day adjustments efficiently. Below, I will break down the solution. Step 1: Define Your TVF First, we need to create the Inline TVF. This will replace the scalar UDF, supporting multiple rows of output rather than a single value. Step 2: Utilize a Tally Table The tally table allows you to generate a sequence of numbers that can serve as indexes for rows in your result set. Here's how the inline TVF looks: [[See Video to Reveal this Text or Code Snippet]] Breakdown of the TVF Parameters: The function accepts a date @D and an integer @I, representing the number of business days to add. Tally Table Creation: We use the master..spt_values system table to create a large enough source for our date calculation without worrying about weekend dates. CTE for Row Numbers: We utilize CTEs to assign row numbers to valid weekdays and filter out weekends efficiently. Returning Results: Finally, we return the date that corresponds with the provided number of business days from the start date. Benefits of Using an Inline TVF Performance: Inline TVFs typically perform better than scalar UDFs because they can be optimized by SQL Server's query processor. Flexibility: You can easily adapt the solution to include holidays or other non-business days by modifying the CTE accordingly. Simplicity: Reducing the complexity of loops makes the code cleaner and easier to maintain. Conclusion Converting a scalar UDF to an Inline TVF is not just about performance; it represents a more modern SQL practice that leverages the powerful features of SQL Server. Although this blog has focused on a specific example, the principle can be applied to many other complex scalar UDFs. By following the structure outlined above, you can streamline your SQL functions and ensure that they run efficiently, setting you up for more complicated scenarios in the future. Happy querying!