# sqlalchemy.orm.exc.MultipleResultsFound: Multiple rows were found for one()

- **ID:** `python/sqlalchemy-orm-query-multiple-results`
- **Domain:** python
- **Category:** runtime_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Using .one() when query returns more than one row.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **Use .one_or_none() if row may not exist.** (95% success)
   ```
   user = session.query(User).filter_by(email='test@test.com').one_or_none()
   ```
2. **Add additional filter to ensure uniqueness.** (90% success)
   ```
   user = session.query(User).filter(User.id == 1).one()
   ```

## Dead Ends

- **Using .first() without checking for uniqueness.** — Returns first row but may miss intended unique row. (70% fail)
- **Catching exception and returning None.** — Hides potential data integrity issues. (60% fail)