Find performance issues
before your users do.

## Performance Assessment: 4/10

## Issues Found

### 🔴 Critical — SUBQUERY_WHERE (Severity 5)
**Finding:** Correlated subqueries in SELECT clause execute once per row.
**Impact:** With 50,000 users, this runs 100,000 subqueries instead of 2 JOINs.
**Fix:**
```sql
-- Before (N+1 pattern)
SELECT u.id, u.email,
  (SELECT COUNT(*) FROM orders o WHERE o.user_id = u.id) AS order_count,
  (SELECT MAX(created_at) FROM orders o WHERE o.user_id = u.id) AS last_order
FROM users u

-- After (single JOIN)
SELECT u.id, u.email,
  COUNT(o.id) AS order_count,
  MAX(o.created_at) AS last_order
FROM users u
LEFT JOIN orders o ON o.user_id = u.id
GROUP BY u.id, u.email
```
**Estimated gain:** 95–99% reduction in logical reads.

### 🟠 High — ORDER_BY_NO_TOP (Severity 1)
**Finding:** ORDER BY without TOP/OFFSET forces a full sort of the result set.
**Recommendation:** Add TOP N or OFFSET/FETCH if only a subset is needed.

## Index Recommendations
```sql
CREATE INDEX IX_orders_user_id_created
ON orders (user_id)
INCLUDE (created_at, id);
```

## Validation Checklist
- [x] Logical reads reduced?
- [x] Functional equivalence confirmed?
- [ ] Test with production data volume