Answer
Stored procedures are precompiled program units that live inside SQL Server. Instead of sending raw SQL text for every request, the application sends only the procedure name and parameters. SQL Server then executes pre-validated logic using a cached execution plan.
Key advantages over raw ad-hoc SQL:
- Reduced network traffic: Only parameter values are sent, not large query strings.
- Plan reuse: SQL Server can cache and reuse execution plans for procedures, reducing compilation overhead and stabilizing performance.
- Centralized business logic: Data-related rules (validation, transformations, audit operations) are centralized and versioned at the database level, simplifying deployments and multi-application integration.
- Security and least-privilege: Applications can be granted EXECUTE rights on procedures instead of direct table access, improving security boundaries and auditability.
- Reduced SQL injection risk: The SQL logic is fixed inside the procedure; parameters are bound, greatly decreasing injection surfaces compared to concatenated SQL strings.