framework/db/sqlite/Schema.php
public function setTransactionIsolationLevel($level)
    {
        switch ($level) {
            case Transaction::SERIALIZABLE:
                $this->db->createCommand('PRAGMA read_uncommitted = False;')->execute();
                break;
            case Transaction::READ_UNCOMMITTED:
                $this->db->createCommand('PRAGMA read_uncommitted = True;')->execute();
                break;
            default:
                throw new NotSupportedException(get_class($this) . ' only supports transaction isolation levels READ UNCOMMITTED and SERIALIZABLE.');
        }
    }
public function setTransactionIsolationLevel($level)
    {
        switch ($level) {
            case Transaction::SERIALIZABLE:
                $this->db->createCommand('PRAGMA read_uncommitted = False;')->execute();
                break;
            case Transaction::READ_UNCOMMITTED:
                $this->db->createCommand('PRAGMA read_uncommitted = True;')->execute();
                break;
            default:
                throw new NotSupportedException(get_class($this) . ' only supports transaction isolation levels READ UNCOMMITTED and SERIALIZABLE.');
        }
    }
Sets the isolation level of the current transaction.
@param string $level The transaction isolation level to use for this transaction.
This can be either [[Transaction::READ_UNCOMMITTED]] or [[Transaction::SERIALIZABLE]].
@throws NotSupportedException when unsupported isolation levels are used.
SQLite only supports SERIALIZABLE and READ UNCOMMITTED.
@see http://www.sqlite.org/pragma.html#pragma_read_uncommitted