results/before_after_table.md

Before / after — execution-grounded reward

Task	Difficulty	Before (no SQL)	After (fallback)	Δ
Basic SQL Anti-pattern Detection	easy	0.4500	0.8300	+0.3800
N+1 Correlated Subquery Elimination	medium	0.4500	0.6900	+0.2400
Wildcard LIKE & Projection Optimization	medium-hard	0.4500	0.6900	+0.2400
Implicit Cross Join & Scalar Subquery El	hard	0.4500	0.6900	+0.2400
Window Function & Full-Scan Audit	expert	0.4500	0.7500	+0.3000

Mean before: 0.4500
Mean after: 0.7300
Mean Δ: +0.2800

Before = non-empty suggestions but optimized_query empty — no speedup/correctness signal.