文档解释
ORA-29884: domain index is defined on the column to be dropped
Cause: An ALTER TABLE DROP COLUMN was issued on a column on which a domain index exists.
Action: Drop the domain index before attempting to drop the column.
ORA-29884错误是指用户删除某列使其上的域索引失效，官方解释如下：
ORA-29884: domain index is defined on the column to be dropped.
Cause: An attempt was made to drop a column which has a domain index defined on it.
Action: Drop all domain indexes before attempting to drop the column.
为了解决ORA-29884错误，应该首先执行DROP INDEX语句删除所有域索引，然后才可以安全的删除指定的列。此外，建议在删除列及索引之前先备份数据库，以防数据丢失。
