mysql的alter语句用法_MySQL

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mysql的alter语句用法 一些语法增加字段：ALTER TABLE table_name ADD field_name field_type; 修改原字段名称及类型：ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;   删除字段：ALTER TABLE table_name DROP field_name 举例修改为自增alter table tb_name modify id int auto_increment primary key 修改字段默认值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) 增加主键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;   加索引alter table tablename add index 索引名 (字段名1[，字段名2 …]);alter table tablename add index emp_name (name); 加主关键字的索引alter table tablename add primary key(id); 加唯一限制条件的索引alter table tablename add unique emp_name2(cardnumber); 删除某个索引5alter table tablename drop index emp_name; bitsCN.com