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

  1. 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 ...

  2. alter table fx.pet modify column `species` varchar(20) binary;

    alter table fx.pet modify column `species` varchar(20) binary;

  3. 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  ...

  4. 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 ...

  5. 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 ...

  6. 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 ...

  7. MySQL中ALTER ,CHANGE , MODIFY

    ALTER TABLE project_list CHANGE COLUMN descriptionofproj proj_desc VARCHAR(100), CHANGE COLUMN contr ...

  8. 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 ...

  9. 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

  1. JavaScript之三：jQuery插件开发(一)

    在早期的开发中,正如前面闭包中所提到的那样,人们一开始并没有意识到要开发出插件这么个玩意儿,都是遇到啥写啥.在长期的工作中,人们发现很多代码是重复的,写了一遍又一遍,以登录页面为例,每写一次都需要重新 ...

  2. HDU--3829--Cat VS Dog【最大点独立集】

    链接:http://acm.hdu.edu.cn/showproblem.php?pid=3829 题意:动物园有n条狗.m头猫.p个小孩,每一个小孩有一个喜欢的动物和讨厌的动物.如今动物园要转移一些 ...

  3. HDU 3081 Marriage Match II（二分法+最大流量）

    HDU 3081 Marriage Match II pid=3081" target="_blank" style="">题目链接 题意:n个 ...

  4. NSIS：制作软件升级安装包

    原文 NSIS:制作软件升级安装包 相信不是每个人写的软件都只发布一次就可以了,肯定要有修改和维护的情况发生.在这种情况下,您可能就需要一个软件的升级安装包了.   现在,我们就来一步步把这个安装包做 ...

  5. linux 文件系统解析及相关命令（转）

    简介 文件系统就是分区或磁盘上的所有文件的逻辑集合. 文件系统不仅包含着文件中的数据而且还有文件系统的结构,所有Linux 用户和程序看到的文件.目录.软连接及文件保护信息等都存储在其中. 不同Lin ...

  6. Gallatin（大陆版）Office365中Exchange Online混合部署功能已经能够使用了

    经过測试,Exchange混合部署已经能够使用了 前置条件: 本机至少须要一台Exchange Server 2013作为混合部署server 须要一个公网域名 domian.com,能够和内部域名不 ...

  7. JAVA多线程编程（详细例子）

    http://wenku.baidu.com/view/e4afbf36a32d7375a417808b.html

  8. three.js 来源目光（十三）Math/Ray.js

    商域无疆 (http://blog.csdn.net/omni360/) 本文遵循"署名-非商业用途-保持一致"创作公用协议 转载请保留此句:商域无疆 -  本博客专注于 敏捷开发 ...

  9. hdu Word Amalgamation（map）

    题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1113 找单词 #include <iostream> #include <strin ...

  10. Android - &quot;cause failed to find target android-14&quot; 问题

    "cause failed to find target android-14" 问题 本文地址: http://blog.csdn.net/caroline_wendy Andr ...