关于修改数据库字段
--在工作中我们会经常碰到临时需要修改数据库中表字段--这里我来给大家介绍下方法，希望能帮助到大家create?table?class_use(??id?number?(19?),??name?varchar2?(50?),??birthday?Date?default?sysdate,??age?number?(19?))?select?*?from?class_use?--for update---通过上面的语句alter?table?CLASS_USE?modify?AGE?varchar2(?19?);---执行时候会报下面的错误--在工作中我们会经常碰到临时需要修改数据库中表字段--这里我来给大家介绍下方法，希望能帮助到大家
??---下面我来介绍2种方式--1.将表备份create?table?class_user_temp?as?select?*?from?class_use;select?*?from?class_user_temp;update?class_use?cset?c?.age?=?null;select?*?from?class_use--再来执行alter?table?CLASS_USE?modify?AGE?varchar2(?19);update?CLASS_USE?ccset?cc?.age?=(?select?temp?.age?from?class_user_temp?temp??????????????where?temp?.id?=?cc.id?);---2.添加字段alter?table?CLASS_USE?add?age1?number(?19);update?CLASS_USE?cset?c?.age1?=?c.age?;select?*?from?CLASS_USEalter?table?CLASS_USE?drop?column?age;alter?table?CLASS_USE?rename?column?AGE1?to?AGE?;?select?*?from?CLASS_USE---下面我来介绍2种方式--1.将表备份create?table?class_user_temp?as?select?*?from?class_use;select?*?from?class_user_temp;update?class_use?cset?c?.age?=?null;select?*?from?class_use--再来执行alter?table?CLASS_USE?modify?AGE?varchar2(?19);update?CLASS_USE?ccset?cc?.age?=(?select?temp?.age?from?class_user_temp?temp??????????????where?temp?.id?=?cc.id?);---2.添加字段alter?table?CLASS_USE?add?age1?number(?19);update?CLASS_USE?cset?c?.age1?=?c.age?;select?*?from?CLASS_USEalter?table?CLASS_USE?drop?column?age;alter?table?CLASS_USE?rename?column?AGE1?to?AGE?;?select?*?from?CLASS_USE
