文档解释
ORA-02449: unique/primary keys in table referenced by foreign keys
Cause: An attempt was made to drop a table with unique or primary keys referenced by foreign keys in another table.
Action: Before performing the above operations the table, drop the foreign key constraints in other tables. You can see what constraints are referencing a table by issuing the following command: SELECT * FROM USER_CONSTRAINTS WHERE TABLE_NAME = “tabnam”;
ORA-02449是Oracle数据库中常见的一类错误，它表示表中被外键所引用的列上缺少了唯一性约束，使外键约束无法应用。
官方解释
ORA-02449 occurs when the column which is referenced by a foreign key constraint does not have a unique or primary key defined.
常见案例
当一个表的行数据的外键子段（Foreign Key Sub-segment）未被设定唯一性约束（唯一性索引或主键索引），而另一张表的某列行数据被该子段引用时，则一般会发生该错误。
正常处理方法及步骤
①查询来源表及相关表后，排查受影响表上缺失的主键/唯一性索引。
②根据查出的信息创建相应的唯一性索引。
③重新执行DDL命令，使外键约束生效。
