Temp Tables Versus Table Variables in SQL Server

Temporary tables and table variables both hold intermediate rows, but statistics, compilation, indexing, and transaction behavior can produce very different execution plans.

What to measure

Measure actual rows, estimates, join choices, spills, recompilations, and repeated access. Deferred compilation helps some table-variable cases but does not make both structures interchangeable.

Practical approach

Use temporary tables for large or variable intermediate sets, add only useful indexes, choose table variables for genuinely small simple sets, and test with production-scale rows and parameter distributions.

What to avoid

Do not choose by syntax preference, assume table variables remain only in memory, or add indexes without considering load cost.

Operational result

Choose the structure that gives the optimizer enough information while keeping intermediate work economical.

Production checklist

Capture a baseline and define the expected improvement. Test with representative data and concurrency. Preserve the original setting or plan, prepare a rollback, deploy during an appropriate window, and monitor the next normal workload peak.

If you want help applying this method to a specific SQL Server environment, use the question form below and include the SQL Server version, database size, workload pattern, and evidence already collected.