22-25 April 2026

Demystifying Clustered Indexes in SQL Server

Proposed session for SQLBits 2026

TL; DR

Explore SQL Server table design choices—heap vs. clustered index. Learn strengths, pitfalls, and practical insights to optimize query speed, storage efficiency, and overall performance.

Session Details

Every SQL Server table tells a story—but whether that story is smooth and efficient or full of performance potholes often depends on a single design choice: should the table be a heap or should it have a clustered index?

In this session, we’ll peel back the layers of how SQL Server organizes data under the hood and shine a light on the differences between heaps and clustered indexes. You’ll see why the decision is more than just a checkbox, and how it can shape everything from query speed to storage efficiency.

We’ll compare the strengths and weaknesses of both approaches, uncover when heaps can actually be the better option, and show where clustered indexes truly deliver their value. Along the way, we’ll expose the hidden pitfalls—like forwarded records and fragmentation—that can quietly erode performance if left unchecked.

If you’ve ever wondered “What really happens to my data when I choose heap vs. clustered index?” this session is for you. Walk away with practical insights, clear models, and the confidence to make smarter choices when designing your SQL Server tables.

3 things you'll get out of this session

- Understand how SQL Server organizes data in heaps vs. clustered indexes and their impact on performance. - Evaluate strengths, weaknesses, and hidden pitfalls (e.g., forwarded records, fragmentation) in both designs. - Apply practical insights and best practices to make informed table design choices for efficiency and scalability.