Think\Db\Builder::parseTable PHP Метод

    protected function parseTable($tables, $options = [])
    {
        $item = [];
        foreach ((array) $tables as $key => $table) {
            if (!is_numeric($key)) {
                $key = $this->parseSqlTable($key);
                $item[] = $this->parseKey($key) . ' ' . $this->parseKey($table);
            } else {
                $table = $this->parseSqlTable($table);
                if (isset($options['alias'][$table])) {
                    $item[] = $this->parseKey($table) . ' ' . $this->parseKey($options['alias'][$table]);
                } else {
                    $item[] = $this->parseKey($table);
                }
            }
        }
        return implode(',', $item);
    }