Temp Table vs Table Variable vs Global Temp Table: A Decision Framework for SQL Server

Three temp object types, three genuinely different jobs. Now that you’ve built all three, here’s how to choose without guessing — and why this exact question shows up so often in interviews.

The Decision Tree

Situational Cheat Sheet

This Is a Genuinely Common Interview Question

“What’s the difference between a temp table and a table variable?” comes up constantly, precisely because the shallow answer (“table variables are smaller/faster”) is folklore, not fact — in practice, on non-trivial row counts, a table variable’s lack of real statistics can make it slower, not faster, exactly because the optimizer’s row estimate is wrong. The strongest interview answer isn’t a definition — it’s the rollback behavior from the previous lesson, because it’s the one difference that actually changes what your code does, not just how fast it runs.

-- A one-line answer worth having ready: "table variables don't roll back with the
-- surrounding transaction, and historically carry no real statistics for the optimizer"
SELECT 'Table variable' AS type, 'Survives rollback, weak statistics' AS behavior
UNION ALL
SELECT 'Temp table', 'Rolls back with transaction, real statistics';