# Transactions

A transaction groups changes into one unit of commit or rollback. Statements outside an explicit transaction autocommit.

## Controls

| Statement          | Effect                                        |
| ------------------ | --------------------------------------------- |
| `BEGIN`            | Start a transaction.                          |
| `COMMIT`           | Keep its changes.                             |
| `ROLLBACK`         | Undo its changes.                             |
| `SAVEPOINT name`   | Create an inner undo point.                   |
| `ROLLBACK TO name` | Undo later changes and retain that savepoint. |
| `RELEASE name`     | Remove the savepoint.                         |

## Example

### Undoing one adjustment

```sql
CREATE TABLE balances(id INTEGER PRIMARY KEY, amount INTEGER);
BEGIN;
INSERT INTO balances VALUES (1, 10);
SAVEPOINT adjustment;
UPDATE balances SET amount = 20;
ROLLBACK TO adjustment;
RELEASE adjustment;
COMMIT;
```

```sql
SELECT id, amount
FROM balances
FORMAT csv;
```

```text
1,10
```

The insert remains, while the adjustment after the savepoint is undone.

## Connection scope

A native connection retains its open transaction. Closing it rolls back uncommitted changes.

Every HTTP request has a separate session. Put BEGIN, the related statements and COMMIT in one request; an unclosed transaction is rolled back before the response is sent.

Several connections in one process can share a file. Simultaneous access from separate processes is outside the supported concurrency model. See [deployment modes](https://coordinatordb.com/docs/get-started/about/deployment-modes).