Learn T-SQL With Erik: Solving Problems With APPLY

Published 13, May 2025

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Description:
In this video, I dive into the beginner section of my upcoming T-SQL course, focusing on the versatile APPLY operator. I start by addressing a common issue that arises when trying to solve top-end-per-group problems using CTEs or derived joins, and then demonstrate how APPLY can elegantly handle these scenarios. By walking through an example with the Stack Overflow database, I explain why certain approaches fail while highlighting the power of APPLY in retrieving the top three badges for users with a reputation over 750,000. The video also delves into the nuances of APPLY's syntax and its two flavors: CROSS APPLY and OUTER APPLY, providing a comprehensive understanding of this powerful T-SQL feature.

CHAPTERS

00:00:00 - Introduction to T-SQL Challenges
00:02:38 - The Problem with the Original Query
00:06:19 - Using APPLY to Solve the Problem
00:07:54 - Explaining the APPLY Syntax and Logic
00:10:45 - Understanding the Starting Query Results
00:11:23 - Applying the Cross Apply Query to Each User
00:12:44 - Using a Derived Join as an Alternative Approach
00:13:59 - Row Number Window Function Explanation
00:15:13 - Performance Considerations and Conclusion

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