Alter API

	function add(string $column): self;
 
	function modify(string $old_column, string $new_column = ''): self;
 
	function drop(string $column): self;
 
    function int(int $size = 255): self;
 
    function bigInt(int $size = 255): self;
 
    function double(int $size = 255, int $d = 2): self;
 
    function boolean(): self;
 
    function string(int $size = 255): self;
 
    function text(int $size = 10000): self;
 
    function longText(int $size): self;
 
	function json(): self;
 
    function required(): self;
 
    function primary($columns = []): self;
 
    function index(array $columns): self;
 
    function date(): self;
 
    function dateTime(): self;
 
	public function timestamp($default = null, $on_update = null): self;
 
    function unsigned(): self;
 
    function autoIncrement(): self;
 
    function default($value): self;
 
	public function enum(array $allowed): self;
 
    function getSql();
 
    function execute();