如何将约束名称添加到已经存在的约束
有没有办法为已经存在的约束命名?
例如:
Is there a way to give names to already existing constraints?
for example :
create table employee (emp_id number(10),emp_name varchar2(20),
dept_id number(10),foreign key(dept_id) references department(dept_id));
在上面的查询中，我没有命名外键约束，所以在创建表后我可以给它命名吗?也可以删除外键约束而不删除列??
In the above query I haven't named the foreign key constraint so after the creation of the table can I give a name to it also can the foreign key constraint be dropped without dropping the column??
推荐答案
是的，您可以像这样重命名约束:alter table t 重命名约束 old_name 为 new_name
Yes you can rename a constraint like this:
alter table t rename constraint old_name to new_name
我忘记了第二个问题.是的，您可以在不删除列的情况下删除约束.如果您不知道约束的名称，您可以在 user_constraints 表中找到它，如下所示:
I've forgotten about the second question. Yes you can drop a constraint without dropping the column. If you do not know the name of the constraint you can find it in user_constraints table like this:
选择约束名称来自 user_constraints其中 table_name = 'your_table'和constraint_type ='R'
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