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= Transactions

This page describes SQL transaction commands supported by the Calcite-based SQL engine.

== SAVEPOINT

Creates a named savepoint in the current transaction.

[source,sql]
----
SAVEPOINT savepointName
----

=== Parameters

- `savepointName` - the name of the savepoint to create.

=== Description

`SAVEPOINT` can be used only inside a transaction.

The command records the current transaction state. Later, you can use `ROLLBACK TO SAVEPOINT` to roll back all transaction changes made after the savepoint was created.

If a savepoint with the same name already exists, `SAVEPOINT` replaces it. The command does not roll back any transaction changes. It removes the previous savepoint with that name and makes the name refer to the current transaction state.

== ROLLBACK TO SAVEPOINT

Rolls back transaction changes to a previously created savepoint.

[source,sql]
----
ROLLBACK TO SAVEPOINT savepointName
----

=== Parameters

- `savepointName` - the name of the savepoint to roll back to.

=== Description

`ROLLBACK TO SAVEPOINT` can be used only inside a transaction.

The command rolls back all transaction changes made after the specified savepoint was created. The transaction remains active and can be committed or rolled back later.

When a transaction is rolled back to a savepoint, savepoints created after the target savepoint are released. The target savepoint remains available and can be used again.

If the specified savepoint does not exist, the command fails.

== Example

[source,sql]
----
INSERT INTO Person(id, name) VALUES (1, 'John');

SAVEPOINT before_update;

UPDATE Person SET name = 'Jane' WHERE id = 1;

ROLLBACK TO SAVEPOINT before_update;
----

After `ROLLBACK TO SAVEPOINT before_update`, the `UPDATE` statement is rolled back, but the preceding `INSERT` statement remains part of the active transaction.