Driver_Database_Driver_MySQLI::_quote_identifier

protected function _quote_identifier($column)
{
    if (is_array($column))

ist($column, $alias) = $column;


    if (is_object($column))
    {
        if ($column instanceof Database)
        {
            // Create a sub-query
            $column = '(' . $column->compile() . ')';
        }
        elseif ($column instanceof Database_Expression)
        {
            // Use a raw expression
            $column = $column->value();
        }
        else
        {
            // Convert the object to a string
            $column = $this->_quote_identifier((string)$column);
        }
    }
se

 转换为字符串
column = trim((string)$column);

f (preg_match('#^(.*) AS (.*)$#i',$column,$m))

   $column = $m[1];
   $alias  = $m[2];


f ($column === '*')

return $column;

lseif (strpos($column, '"') !== false)

// Quote the column in FUNC("column") identifiers
$column = preg_replace('/"(.+?)"/e', '$this->_quote_identifier("$1")', $column);

lseif (strpos($column, '.') !== false)

$parts = explode('.', $column);

$prefix = $this->config['table_prefix'];
if ($prefix)
{
	// Get the offset of the table name, 2nd-to-last part
	$offset = count($parts) - 2;

                if (!$this->_as_table || !in_array($parts[$offset],$this->_as_table))
                {
                    $parts[$offset] = $prefix . $parts[$offset];
                }
}

foreach ($parts as & $part)
{
	if ($part !== '*')
	{
		// Quote each of the parts
	    $this->_change_charset($part);
		$part = $this->_identifier . str_replace($this->_identifier, '', $part) . $this->_identifier;
	}
}

$column = implode('.', $parts);

lse

   $this->_change_charset($column);
$column = $this->_identifier . str_replace($this->_identifier, '', $column) . $this->_identifier;



 (isset($alias))

  $this->_change_charset($alias);
column .= ' AS ' . $this->_identifier . str_replace($this->_identifier,'',$alias).$this->_identifier;


turn $column;
}