framework/db/Query.php
public function one($db = null)
    {
        if ($this->emulateExecution) {
            return false;
        }

        return $this->createCommand($db)->queryOne();
    }
public function one($db = null)
    {
        if ($this->emulateExecution) {
            return false;
        }

        return $this->createCommand($db)->queryOne();
    }
Executes the query and returns a single row of result.
@param Connection $db the database connection used to generate the SQL statement.
If this parameter is not given, the `db` application component will be used.
@return array|bool the first row (in terms of an array) of the query result. False is returned if the query
results in nothing.