SQL: What is Halloween protection?
If you’ve worked with SQL Server (or with databases in general) for any length of time, you will have heard someone refer to Halloween protection. It refers to a problem where update operations could inadvertently end up modifying a row more than once.
Why halloween?
The name Halloween protection comes from when the problem occurred during research on the System R project at the IBM Almaden Research Center back in 1976.
2025-05-30