如何在 ALTER TABLE 语句中添加“ON DELETE CASCADE"
我的表中有一个外键约束,我想向它添加 ON DELETE CASCADE.
我已经试过了:
<前>更改表 child_table_name修改约束 fk_name外键(child_column_name)在删除级联上引用 parent_table_name (parent_column_name);不起作用.
外键已存在,外键列有数据.
执行语句后得到的错误信息:
<前>ORA-02275: 表中已存在此类引用约束 解决方案您不能将 ON DELETE CASCADE
添加到已存在的约束中.您必须drop
并重新create
约束.文档a> 显示MODIFY CONSTRAINT
子句只能修改约束状态(即:ENABLED/DISABLED
...).
I have a foreign key constraint in my table, I want to add ON DELETE CASCADE to it.
I have tried this:
alter table child_table_name modify constraint fk_name foreign key (child_column_name) references parent_table_name (parent_column_name) on delete cascade;
Doesn't work.
EDIT:
Foreign key already exists, there are data in foreign key column.
The error message I get after executing the statement:
ORA-02275: such a referential constraint already exists in the table
解决方案
You can not add ON DELETE CASCADE
to an already existing constraint. You will have to drop
and re-create
the constraint. The documentation shows that the MODIFY CONSTRAINT
clause can only modify the state of a constraint (i-e: ENABLED/DISABLED
...).
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