How to Create a Scalar Function in SQL Server to Add Business Days using SMALLDATETIME

Discover how to effectively calculate and return a `SMALLDATETIME` value with a scalar function in SQL Server, including practical steps and important tips for beginners.
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Adding Business Days in SQL Server: A Guide to Using Scalar Functions

In the world of SQL Server, handling dates and times can sometimes become complex, especially when you need to calculate future dates based on business days. If you've ever wondered how to create a scalar function that calculates a date a given number of business days forward, you're not alone! Many developers face this challenge. In this guide, we will walk you through how to create such a function using the SMALLDATETIME datatype in SQL Server.

Understanding the Problem

Imagine you have a calendar table that marks weekends and holidays, and you want to create a function that takes a starting date and a number of business days to add. The goal is to return the future date while ensuring that weekends and holidays are excluded from the count.

Here’s a simplified overview of what you're looking to achieve:

Input: A starting date (@ startDate) and the number of business days you want to add (@ numBusDays).

Output: A future date that skips any non-business days (weekends and holidays).

Creating the Scalar Function

To create this scalar function in SQL Server, follow the detailed steps below. We'll utilize a calendar table named OurCalendar that indicates whether a day is a weekday or a holiday.

Step 1: Function Signature

Begin defining your function. This will include the input parameters and the return type:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Handling the Start Date

Next, you’ll want to check if the provided starting date is a business day. This check will determine if you need to include it when counting the number of business days:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Select the Future Date

Now it's time to select the future date. You will query your calendar table to find the next business days. Note that we're adding @ workdayModifier to account for the start date correctly:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Return the Result

Finally, you will return the calculated date. Your complete function should look like this:

[[See Video to Reveal this Text or Code Snippet]]

When combined, the full function becomes:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

In summary, creating a scalar function in SQL Server that returns a SMALLDATETIME value by adding business days is straightforward once you understand the underlying logic. By carefully checking if the start date is a business day and querying the right information from your calendar table, you can effectively achieve your goal.

The steps we've covered should help you build a robust solution to manage business dates in your SQL applications, enhancing your scheduling and planning functionalities.

Feel free to reach out if you have any questions or need further assistance with SQL Server functions!