Sql-Server

When one step in a multi-step SQL Server script fails, what actually happens to your data depends entirely on how you’ve wired up error handling, and the default is not what most people assume. Three scenarios, measured with real ledger output.

A join rule that matches ‘anything’ looks like an ordinary filter, until it quietly multiplies your row count. Measured, not estimated: what a wildcard join actually costs, why a CREATE INDEX line doesn’t always buy you a seek, and why UNPIVOT beats a ten-way OR chain.