MYSQL SQL statements that modify table structure

1. Background

　　Use sql statement to modify table structure

2. Case presentations

Case: table structure
 the CREATE  TABLE `login_user` (
  `id` int(32) NOT NULL AUTO_INCREMENT,
  `name` varchar(225) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL COMMENT '名字',
  password` ` VARCHAR ( 26 is ) the DEFAULT  NULL the COMMENT " password 3 ' ,
  `type` varchar(32) DEFAULT NULL,
  `state` varchar(32) DEFAULT NULL,
  `create_time` datetime DEFAULT NULL,
  `update_time` datetime DEFAULT NULL,
  `password5` varchar(26) DEFAULT NULL COMMENT '密码5',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;


1 . Modify Field: General data types and modify the properties

alter table login_user modify password varchar(25) DEFAULT NULL COMMENT '密码2'

2 . Rename fields: ALTER  Table table name change field data type field of the new and old [ attributes ] [ position ] ;

alter table login_user change password2  password varchar(26) DEFAULT NULL COMMENT '密码3'

3 . New field: ALTER   Table   table   the Add  [ column ]   Field Name Data Type   [ Column Properties ] [ position ]
Location: anywhere in the field may be stored in the table;
first: the first position;
after: After which field; default after the last field.

- added to final 
ALTER   Table   login_user   the Add    password3   VARCHAR ( 26 is ) the DEFAULT  NULL the COMMENT " password 4 ' 
- add a field to the field name specified later alter table + + add + table name field type field to be added to follow the + after + 
ALTER   Table   login_user   the Add    password6    VARCHAR ( 26 is )   the DEFAULT  NULL the COMMENT ' password. 6 '   After password

4 Remove fields: the ALTER  the Table table name drop field names;

alter  table  login_user  drop   password5