mysql alter语句用法举例

发布时间:2020-12-11编辑:脚本学堂
mysql alter语句用法举例,供大家学习参考。//主键 ALTER TABLE tablename add new_field_id int(5) UNSIGNED DEFAULT 0 NOT NULL anto_increment,ADD PRIMARY KEY (new_field_id);

mysql alter语句用法举例,供大家学习参考。

//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;