AliasedQuery::addAlias

public function addAlias($alias, $field = null)
{
	if (($this->aliases[$alias] ?? false))
	{
		throw new SystemException("`$alias` already added", 0, __FILE__, __LINE__);
	}
	elseif (! $field)
	{
		$this->aliases[$alias] = $alias;
	}
	elseif (is_string($field) || (is_array($field) && $field['expression'])) // TODO Field support
	{
		$this->aliases[$alias] = $field;
	}
	else
	{
		throw new SystemException("invalid `$alias` type", 0, __FILE__, __LINE__);
	}

	return $this;
}