mysql alter table 语法实例讲解

ALTER TABLE table_name ADD field_name field_type;

ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

ALTER TABLE table_name DROP field_name

alter table tb_name modify id int auto_increment primary key

alter table tablename alter column drop default; (若本身存在默认值，则先删除)
alter table tablename alter column set default 't5';(若本身不存在则可以直接设定)

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

alter table t2 add d timestamp;
alter table infos add ex tinyint not null default '0';

alter table t2 drop column c;

alter table t1 change a b integer;

alter table t1 change b b bigint not null;
alter table infos change list list tinyint not null default '0';

alter table t1 rename t2;

alter table tablename add index 索引名 (字段名1[，字段名2 …]);
alter table tablename add index emp_name (name);

alter table tablename add primary key(id);

alter table tablename add unique emp_name2(cardnumber);

alter table tablename drop index emp_name;