Learn T-SQL With Erik: Getting Defensive with CASE Expressions

Published 28, May 2025

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Description:
In this video, I delve into the importance of defensive case expressions in SQL Server queries, particularly focusing on how they can prevent unexpected errors and maintain query reliability. I illustrate this through a practical example where we create a simple table and run a basic percentage calculation query. However, as the transcript highlights, even with straightforward data, issues like division by zero can arise if unexpected values sneak into your database. To address these challenges, I demonstrate how to use case expressions and nullif functions to handle such scenarios gracefully, ensuring that our queries remain robust and error-free. By emphasizing defensive coding practices, we avoid potential disasters, such as ETL processes failing in the middle of the night due to unforeseen errors.

CHAPTERS

00:00:00 - Introduction
00:00:29 - Defensive Case Expressions
00:01:25 - Creating a Table Example
00:01:51 - Unexpected Data Issues
00:02:25 - Implicit Conversion Problems
00:03:18 - Divide by Zero Error
00:03:58 - Using Case Expressions
00:04:35 - Nullif Function Alternative
00:05:30 - Writing Defensively
00:06:25 - Preventing Surprises

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