Database Query Debugger

Help me debug this SQL query:

**Query:**
```sql
{{QUERY}}
```

**Expected Result:** {{EXPECTED_RESULT}}
**Actual Result:** {{ACTUAL_RESULT}}

**Sample Data:**
```sql
{{SAMPLE_DATA}}
```

**Database System:** {{DATABASE_SYSTEM}}

Please:
1. Identify the issue(s) in the query
2. Explain why the query produces unexpected results
3. Provide the corrected query
4. Step-by-step breakdown of query execution
5. Test cases to verify the fix
6. Common pitfalls to avoid in similar queries