13.3.3 Statements That Cause an Implicit Commit

The statements listed in this section (and any synonyms for them) implicitly end any transaction active in the current session, as if you had done a COMMIT before executing the statement.

Most of these statements also cause an implicit commit after executing. The intent is to handle each such statement in its own special transaction because it cannot be rolled back anyway. Transaction-control and locking statements are exceptions: If an implicit commit occurs before execution, another does not occur after.