MySQL之 ALTER vs CHANGE vs MODIFY COLUMN

1.ALTER COLUMN

用于设置或者移除某一列的默认（缺省）值，

1.1用法

ALTER TABLE MyTable ALTER COLUMN foo SET DEFAULT 'bar';

ALTER TABLE MyTable ALTER COLUMN foo DROP DEFAULT;

1.2 举例

mysql> desc pre_common_block;

+----------------+-----------------------+------+-----+---------+----------------+

| Field          | Type                  | Null | Key | Default | Extra          |

+----------------+-----------------------+------+-----+---------+----------------+

| bid            | mediumint(8) unsigned | NO   | PRI | NULL    | auto_increment |

| blockclass     | varchar(255)          | NO   |     | 0       |                |

| blocktype      | tinyint(1)            | NO   |     | 0       |                |

| name           | varchar(255)          | NO   |     |         |                |

| title          | text                  | NO   |     | NULL    |                |

| classname      | varchar(255)          | NO   |     |         |                |

| summary        | text                  | NO   |     | NULL    |                |

| uid            | mediumint(8) unsigned | NO   |     | 0       |                |

| username       | varchar(255)          | NO   |     |         |                |

| styleid        | smallint(6) unsigned  | NO   |     | 0       |                |

| blockstyle     | text                  | NO   |     | NULL    |                |

| picwidth       | smallint(6) unsigned  | NO   |     | 0       |                |

| picheight      | smallint(6) unsigned  | NO   |     | 0       |                |

| target         | varchar(255)          | NO   |     |         |                |

| dateformat     | varchar(255)          | NO   |     |         |                |

| dateuformat    | tinyint(1)            | NO   |     | 0       |                |

| script         | varchar(255)          | NO   |     |         |                |

| param          | text                  | NO   |     | NULL    |                |

| shownum        | smallint(6) unsigned  | NO   |     | 0       |                |

| cachetime      | int(10)               | NO   |     | 0       |                |

| cachetimerange | char(5)               | NO   |     |         |                |

| punctualupdate | tinyint(1)            | NO   |     | 0       |                |

| hidedisplay    | tinyint(1)            | NO   |     | 0       |                |

| dateline       | int(10) unsigned      | NO   |     | 0       |                |

| notinherited   | tinyint(1)            | NO   |     | 0       |                |

| isblank        | tinyint(1)            | NO   |     | 0       |                |

+----------------+-----------------------+------+-----+---------+----------------+

26 rows in set (0.14 sec)

mysql> ALTER TABLE pre_common_block  ALTER COLUMN  blocktype set  DEFAULT 5;

Query OK, 0 rows affected (0.32 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> desc pre_common_block;

+----------------+-----------------------+------+-----+---------+----------------+

| Field          | Type                  | Null | Key | Default | Extra          |

+----------------+-----------------------+------+-----+---------+----------------+

| bid            | mediumint(8) unsigned | NO   | PRI | NULL    | auto_increment |

| blockclass     | varchar(255)          | NO   |     | 0       |                |

| blocktype      | tinyint(1)            | NO   |     | 5       |                |

| name           | varchar(255)          | NO   |     |         |                |

| title          | text                  | NO   |     | NULL    |                |

| classname      | varchar(255)          | NO   |     |         |                |

| summary        | text                  | NO   |     | NULL    |                |

| uid            | mediumint(8) unsigned | NO   |     | 0       |                |

| username       | varchar(255)          | NO   |     |         |                |

| styleid        | smallint(6) unsigned  | NO   |     | 0       |                |

| blockstyle     | text                  | NO   |     | NULL    |                |

| picwidth       | smallint(6) unsigned  | NO   |     | 0       |                |

| picheight      | smallint(6) unsigned  | NO   |     | 0       |                |

| target         | varchar(255)          | NO   |     |         |                |

| dateformat     | varchar(255)          | NO   |     |         |                |

| dateuformat    | tinyint(1)            | NO   |     | 0       |                |

| script         | varchar(255)          | NO   |     |         |                |

| param          | text                  | NO   |     | NULL    |                |

| shownum        | smallint(6) unsigned  | NO   |     | 0       |                |

| cachetime      | int(10)               | NO   |     | 0       |                |

| cachetimerange | char(5)               | NO   |     |         |                |

| punctualupdate | tinyint(1)            | NO   |     | 0       |                |

| hidedisplay    | tinyint(1)            | NO   |     | 0       |                |

| dateline       | int(10) unsigned      | NO   |     | 0       |                |

| notinherited   | tinyint(1)            | NO   |     | 0       |                |

| isblank        | tinyint(1)            | NO   |     | 0       |                |

+----------------+-----------------------+------+-----+---------+----------------+

26 rows in set (0.02 sec)

2.ALTER COLUMN

用于某一数据列的重命名、修改数据类型或者删除。

2.1用法

ALTER TABLE MyTable CHANGE COLUMN foo bar VARCHAR(32) NOT NULL FIRST;

ALTER TABLE MyTable CHANGE COLUMN foo bar VARCHAR(32) NOT NULL AFTER baz;

2.2 举例

mysql> desc pre_common_block;

+----------------+-----------------------+------+-----+---------+----------------+

| Field          | Type                  | Null | Key | Default | Extra          |

+----------------+-----------------------+------+-----+---------+----------------+

| bid            | mediumint(8) unsigned | NO   | PRI | NULL    | auto_increment |

| blockclass     | varchar(255)          | NO   |     | 0       |                |

| blocktype      | tinyint(1)            | NO   |     | 5       |                |

| name           | varchar(255)          | NO   |     |         |                |

| title          | text                  | NO   |     | NULL    |                |

| classname      | varchar(255)          | NO   |     |         |                |

| summary        | text                  | NO   |     | NULL    |                |

| uid            | mediumint(8) unsigned | NO   |     | 0       |                |

| username       | varchar(255)          | NO   |     |         |                |

| styleid        | smallint(6) unsigned  | NO   |     | 0       |                |

| blockstyle     | text                  | NO   |     | NULL    |                |

| picwidth       | smallint(6) unsigned  | NO   |     | 0       |                |

| picheight      | smallint(6) unsigned  | NO   |     | 0       |                |

| target         | varchar(255)          | NO   |     |         |                |

| dateformat     | varchar(255)          | NO   |     |         |                |

| dateuformat    | tinyint(1)            | NO   |     | 0       |                |

| script         | varchar(255)          | NO   |     |         |                |

| param          | text                  | NO   |     | NULL    |                |

| shownum        | smallint(6) unsigned  | NO   |     | 0       |                |

| cachetime      | int(10)               | NO   |     | 0       |                |

| cachetimerange | char(5)               | NO   |     |         |                |

| punctualupdate | tinyint(1)            | NO   |     | 0       |                |

| hidedisplay    | tinyint(1)            | NO   |     | 0       |                |

| dateline       | int(10) unsigned      | NO   |     | 0       |                |

| notinherited   | tinyint(1)            | NO   |     | 0       |                |

| isblank        | tinyint(1)            | NO   |     | 0       |                |

+----------------+-----------------------+------+-----+---------+----------------+

26 rows in set (0.02 sec)

mysql> ALTER TABLE pre_common_block CHANGE COLUMN  blocktype  changetype tinyint(1)  NOT NULL

Query OK, 2 rows affected (0.77 sec)

Records: 2  Duplicates: 0  Warnings: 0

mysql> desc pre_common_block;

+----------------+-----------------------+------+-----+---------+----------------+

| Field          | Type                  | Null | Key | Default | Extra          |

+----------------+-----------------------+------+-----+---------+----------------+

| changetype     | tinyint(1)            | NO   |     | NULL    |                |

| bid            | mediumint(8) unsigned | NO   | PRI | NULL    | auto_increment |

| blockclass     | varchar(255)          | NO   |     | 0       |                |

| name           | varchar(255)          | NO   |     |         |                |

| title          | text                  | NO   |     | NULL    |                |

| classname      | varchar(255)          | NO   |     |         |                |

| summary        | text                  | NO   |     | NULL    |                |

| uid            | mediumint(8) unsigned | NO   |     | 0       |                |

| username       | varchar(255)          | NO   |     |         |                |

| styleid        | smallint(6) unsigned  | NO   |     | 0       |                |

| blockstyle     | text                  | NO   |     | NULL    |                |

| picwidth       | smallint(6) unsigned  | NO   |     | 0       |                |

| picheight      | smallint(6) unsigned  | NO   |     | 0       |                |

| target         | varchar(255)          | NO   |     |         |                |

| dateformat     | varchar(255)          | NO   |     |         |                |

| dateuformat    | tinyint(1)            | NO   |     | 0       |                |

| script         | varchar(255)          | NO   |     |         |                |

| param          | text                  | NO   |     | NULL    |                |

| shownum        | smallint(6) unsigned  | NO   |     | 0       |                |

| cachetime      | int(10)               | NO   |     | 0       |                |

| cachetimerange | char(5)               | NO   |     |         |                |

| punctualupdate | tinyint(1)            | NO   |     | 0       |                |

| hidedisplay    | tinyint(1)            | NO   |     | 0       |                |

| dateline       | int(10) unsigned      | NO   |     | 0       |                |

| notinherited   | tinyint(1)            | NO   |     | 0       |                |

| isblank        | tinyint(1)            | NO   |     | 0       |                |

+----------------+-----------------------+------+-----+---------+----------------+

26 rows in set (0.00 sec)

3.MODIFY COLUMN

除了重命名外能够做CHANGE COLUMN能做的一切工作。

3.1用法

ALTER TABLE MyTable MODIFY COLUMN foo VARCHAR(32) NOT NULL AFTER baz;

MySQL之 ALTER vs CHANGE vs MODIFY COLUMN的更多相关文章

MySQL ALTER TABLE: ALTER vs CHANGE vs MODIFY COLUMN
ALTER COLUMN 语法: ALTER [COLUMN] col_name {SET DEFAULT literal | DROP DEFAULT} 作用: 设置或删除列的默认值.该操作会直接修 ...
alter table fx.pet modify column `species` varchar(20) binary;
alter table fx.pet modify column `species` varchar(20) binary;
mysql ALTER COLUMN MODIFY COLUMN CHANGE COLUMN 区别及用法 (转)
-- 设置或删除列的默认值.该操作会直接修改.frm文件而不涉及表数据.此操作很快 -- ALTER COLUMN ALTER TABLE dsp_ad_center.XianDuan ALTER ...
mysql 的 alter table 操作性能小提示
通常情况下,修改表的结构一般不会有太大问题,无非就是一个 alter table 操作,但是对于大表做 alter 操作是一个大问题,请小伙伴们慎重. mysql执行大部分修改表结构操作方法是创建一个 ...
mysql之ALTER COLUMN、CHANGE COLUMN、MODIFY COLUMN的区别
ALTER COLUMN:设置或删除列的默认值(操作速度非常快) 例子: alter table film alter column rental_duration set default 5; al ...
MySQL：ALTER COLUMN、MODIFY COLUMN 和 CHANGE COLUMN
ALTER COLUMN.MODIFY COLUMN 和 CHANGE COLUMN 语句修改列: ALTER COLUMN:改变.删除列的默认值(备注:列的默认值存储在 .frm 文件中). 这个语 ...
MySQL中ALTER ,CHANGE , MODIFY
ALTER TABLE project_list CHANGE COLUMN descriptionofproj proj_desc VARCHAR(100), CHANGE COLUMN contr ...
mysql 中alter语句中change跟modify的区别
mysql 中alter语句中change和modify的区别可以使用CHANGE old_col_name column_definition子句对列进行重命名.重命名时,需给定旧的和新的列名称和列 ...
Modify column Vs change column
引言 I know, we can not rename a column using modify column syntax,but can change column syntax. My qu ...

随机推荐

tomcatserver解析（六）-- Acceptor
Acceptor负责用来管理连接到tomcatserver的数量,来看看Acceptor在tomcatserver中的应用,是怎样实现连接管理的,socket连接建立成功之后,是怎样实现内容的读写的( ...
HTTP工作原理
HTTP工作过程 HTTP协议定义Webclient怎样从Webserver请求Web页面,以及server怎样把Web页面传送给client.HTTP协议採用了请求/响应模型. client向 ...
cocos2d-x3.2中map的基本操作和使用
在游戏开发中,我们有时候会用到map,而map的使用方法我简单给大家介绍一下.Map是c++的一个标准容器,她提供了非常好一对一的关系,在一些程序中建立一个map能够起到事半功倍的效果,总结了一些ma ...
log4j的配置信息（转）
首先,在项目中的classes 中新建立一个log4j.properties文件即可: 在实际编程时,要使Log4j真正在系统中运行事先还要对配置文件进行定义.定义步骤就是对Logger.Append ...
android_线
说明:android螺纹. android无非就是一个线程Main Thread和Worker Thread.(除了主线程Main Thread是Worker Thread) Main Thread ...
解决 configure.ac:17: error: possibly undefined macro: AC_PROG_LIBTOOL
当安装configure.ac:17: error: possibly undefined macro: AC_PROG_LIBTOOL If this token and others are le ...
用Markdown来写作
Markdown 是一种简单的.轻量级的标记语法.github上面很多的README就是用markdonw语法写的. Markdown 的语法十分简单,常用的标记符号也不超过十个,且一旦熟悉这种语法规 ...
Lampda或Linq中的SqlFunctions.StringConvert()
要使用 Lampda或Linq中的SqlFunctions.StringConvert(), 需要引用命名空间using System.Data.Objects.SqlClient, 该函数可进行模拟 ...
网络资源(3) - iBatis视频
2018_08_24 http://v.youku.com/v_show/id_XMjk2ODY2OTE2.html iBatis视频教程01
第14章命令模式（Command Pattern）
原文第14章命令模式(Command Pattern) 命令模式(Command Pattern) 概述在软件系统中,“行为请求者”与“行为实现者”通常呈现一种“紧耦合”.但在某些场合,比如 ...

MySQL之 ALTER vs CHANGE vs MODIFY COLUMN

1.ALTER COLUMN

2.ALTER COLUMN

3.MODIFY COLUMN

MySQL之 ALTER vs CHANGE vs MODIFY COLUMN的更多相关文章

随机推荐

热门专题