mysql alter语句用法

//主键ALTER TABLE tablename add new_field_id int(5) UNSIGNED DEFAULT 0 NOT NULL anto_increment,ADD PRIMARY KEY (new_field_id);//增加一个新列mysql>ALTER TABLE tablename ADD fieldname fieldtype如：ALTER TABLE t2 ADD d TIMESTAMP;ALTER TABLE infos ADD ex TINYINT NOT NULL DEFAULT '0';//删除列mysql>ALTER TABLE table_name DROP field_name如：ALTER TABLE t2 DROP COLUMN c;//修改原字段名称及类型mysql>ALTER TABLE tablename CHANGE old_field_name new_field_name field_type;如：//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);//加主关键字的搜索mysql>ALTER TABLE tablename ADD PRIMARY KEY(id);//加唯一限制条件的索引mysql>ALTER TABLE tablename ADD UNIQUE emp_name2(cardnumber);//删除某个索引mysql>ALTER TABLE tablename DROP INDEX emp_name;