增加一列到某列名后
alter table table_name add column_name int after column_name;

改变列名称
alter table table_name change old_column_name new_column_name int;

修改类型
alter table table_name modify column_name float;

删除列
alter table table_name drop column_name;

修改表名
alter table old_table_name rename new_table;

表结构的删除
drop table table_name(注意外键的情况) with check option

添加主键
alter table table_name add primary key(COLUMN1,COLUMN2);

删除主键
alter table table_name drop primary key;

添加约束
alter table table_name add unique(COLUMN_name);

删除约束
alter table table_name drop index column_name;

MySQL基础语法