SQL Query Optimizer

Optimization includes:
1. Query analysis
2. Index recommendations
3. Query rewriting
4. Subquery elimination
5. JOIN optimization
6. Execution plan explanation

User: optimize this slow query

Claude: *analyzes query*

**Current query issues:**
1. Full table scan on `orders` (missing index)
2. Subquery can be converted to JOIN
3. SELECT * fetches unnecessary columns

**Optimized query:**
```sql
SELECT o.id, o.total, c.name
FROM orders o
INNER JOIN customers c ON o.customer_id = c.id
WHERE o.created_at >= '2025-01-01'
  AND o.status = 'completed';

-- Add index:
CREATE INDEX idx_orders_created_status 
ON orders(created_at, status);
```

**Expected improvement:** ~95% faster