6 第二种方法是，已经创建好表了，我们为表字段设置了默认值，首先我们先把第一种方法的reader_sex为默认值男删除，让它恢复为初始状态的sql语句为：use library;alter table book change reader_sex reader_sex char(2) null;点击闪电标志的按钮，执行sql语句 7 查看一下表结构，reader_
mysql> alter table t3 change a a int(5) unsigned zerofill; mysql> show create table t3\G *** 1. row *** Table: t3 Create Table: CREATE TABLE `t3` ( `a` int(5) unsigned zerofill DEFAULT NULL, --具有了zerofill `b` int(10) unsigned DEFAULT NULL ) ENGINE=MyISAM DEFAULT CHARSET...
ALTER TABLE dept CHANGE birth employee_birth VARCHAR(100); 1. 四:修改 sex 字段,数据类型为 CHAR (1),非空约束。 ALTER TABLE dept MODIFY sex CHAR(1) NOT NULL; 1. 五:删除字段 note ALTER TABLE dept DROP note; 1. 六:增加字段名 favoriate_activity ,数据类型为 VARCHAR (100)。 ALTER TABLE ...
Now that MySQL 5.1 is not supported any more, it makes no sense to use any other value than innodb_large_prefix=ON. Basically, the only purpose of innodb_file_format and innodb_large_prefix is to cripple the capabilities of InnoDB. This is the reason to change the default values to ‘...
Bug #12948 Change of default value of (datetime) column to NULL not recognised Submitted: 2 Sep 2005 11:37Modified: 27 Sep 2005 16:48 Reporter: Peter Velens Email Updates: Status: Closed Impact on me: None Category: MySQL AdministratorSeverity: S3 (Non-critical) Version: 1.1.2OS: ...
1.容灾备份恢复必备条件MySQL 数据库开启了log-bin参数记录binlog日志功能,且主库于备份的从库都要开启binlo功能。 1.全量备份全量数据就是数据库中所有的数据,全量备份就是把数据库中所有的数据进行备份。 案例: 代码语言:javascript 代码运行次数:0
create table my_goods( 字段… )default charset utf8; 2、如果数据表中已经添加了数据,则可以通过alter table ... change/modify完成对表字段字符集的设置。如下,修改my_goods数据表中的name为例: 🍎为部分字段添加数据 除了为数据表中所有字段添加数据外,还可以通过指定字段名的方式增加数据。其中,指定字段名...
figured you all would want to be aware that this is happening. Maybe you didn't intend to change the default value of this property or assumed there would be no compatibility issues. Reading through the connector's changelogs, it looks like the property and its default value were introduced...
AnALTER TABLEstatement that changes the default value of a columncol_namemay also change the value of a generated column expression that refers to the column usingcol_name, which may change the value of a generated column expression that refers to the column usingDEFAULT(col_name). For this ...
1. default 概念 指定某列的默认值,插入数据时候,此列没有值,则用default指定的值来填充 添加 在创建表的时候添加: create … default create table t1( id int default 1, name varchar(20) default ‘老王’); 通过alter语句添加: alter … modify/change … alter table t1 modify id int default 2; ...