If you d like to know where visitors to your site live, ADD this to your feedback forms. They just choose a region, and the second menu changes appropriately, allowing them to choose their country. (If they choose USA, it allows them to select their state) Neat!
alter table tbl_name ADD col_name type
例如,給表增加一列weight
mysql>alter table pet ADD weight int
刪除列
alter table tbl_name drop col_name
例如，刪除列weight：
mysql>alter table pet drop weight
改變列
alter table tbl_name modify col_name type
例如，改變weight的類型：
mysql> alter table pet modify weight samllint
另一種方法是：
alter table tbl_name change old_col_name col_name type
例如：
mysql> alter table pet change weight weight samllint
給列更名
mysql>alter table pet change weight wei
給表更名
alter table tbl_name rename new_tbl
例如，把pet表更名為animal
mysql>alter table pet rename animal
