DuckDB's existing EXPLAIN output shows operator details but not executable SQL, limiting inspection and tooling that rely on query rewrites and plan structure.

The internal optimized logical plans were not exposed as standalone SQL queries, making it difficult to analyze, reuse, or isolate parts of optimized queries outside DuckDB's internal representations.

Implemented EXPLAIN (SQL) that reconstructs optimized logical plans into executable DuckDB SQL queries, preserving column names, types, and logical semantics, while reflecting optimizer rewrites such as join reordering and expression simplification.

Exposing optimized plans as executable SQL enables better query analysis, debugging, and tooling without depending on internal plan formats, but requires careful rebinding under current catalog and settings to ensure semantic equivalence.