学习mysql的alter语句的用法：添加、修改、删除字段等

//主键
alter table tabelname add new_field_id int(5) unsigned default 0 not null auto_increment ,add primary key (new_field_id);

//增加一个新列
alter table t2 add d timestamp;
alter table infos add ex tinyint not null default '0';

//删除列
alter table t2 drop column c;

//重命名列
alter table t1 change a b integer;

//改变列的类型
alter table t1 change b b bigint not null;
alter table infos change list list tinyint not null default '0';

//重命名表
alter table t1 rename t2;

mysql> alter table tablename change depno depno int(5) not null;
mysql> alter table tablename add index 索引名 (字段名1[，字段名2 …]);
mysql> alter table tablename add index emp_name (name);

mysql> alter table tablename add primary key(id);

mysql> alter table tablename add unique emp_name2(cardnumber);

mysql>alter table tablename drop index emp_name;

mysql> ALTER TABLE table_name ADD field_name field_type;

mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

mysql> ALTER TABLE table_name DROP field_name;