Introduction
As DBAs, we often think of INCLUDE columns as a harmless way to cover queries.They aren’t part of the index key, so it’s easy to assume that adding them wouldn’t have much impact.
This thinking is dangerously incomplete. While INCLUDE columns don’t participate in index order, they physically reside in index leaf rows. The silent impact of this design choice became crystal clear in a recent experiment I ran to test how INCLUDE columns affect transaction log generation during updates.
INCLUDE columns only: When you update columns that are