sql-optimizerlisted

# SQL Optimizer Optimize the SQL for: **$ARGUMENTS** ## Steps 1. **Parse the query** — Read the SQL and understand: - What data is being requested - Join structure and cardinality - Filter conditions and their selectivity - Aggregations and groupings - Subqueries and CTEs 2. **Identify performance issues**: | Issue | Symptom | Fix | |-------|---------|-----| | Full table scan | No WHERE clause index match | Add index or rewrite filter | | SELECT * | Fetching unused columns | Select only needed columns | | Correlated subquery | Subquery runs per row | Rewrite as JOIN or CTE | | Implicit type cast | Filter on wrong type | Cast explicitly or fix schema | | Missing JOIN index | Slow JOIN on unindexed column | Add index on join column | | Unnecessary DISTINCT | Masking a join issue | Fix the join instead | | ORDER BY + LIMIT without index | Sort on full result set | Add composite index | | N+1 in application | Multiple queries in loop | Use JOIN or IN clause | 3. **Rewrite the query** — Produce an optimized version with: - Clear CTEs instead of nested subqueries - Proper index utilization - Minimal data fetched - Comments explaining non-obvious choices 4. **Suggest schema changes** if needed: - Indexes that would help this query - Materialized views for expensive aggregations - Partitioning for large table scans 5. **Estimate impact** — Qualitative assessment: - "This eliminates a full table scan on a ~1M