ORA-02298 Parent Keys Not Found?

问题:

I've been stuck on this for ages as every time I try it - it comes up with the following error: Cannot Validate - parent keys not found.

Here's the code (http://i.imgur.com/6JBzTiM.jpg):

I can create the Primary Key in the Employees table and assign it to EmployeeId. But when trying to add that as a foreign key in the WorkPackages table (using the code below)

ALTER TABLE WORKPACKAGES ADD FOREIGN KEY (EMPLOYEEID) REFERENCES EMPLOYEES (EMPLOYEEID); 

it keeps on coming up with the validation error.

What am I doing wrong?

回答1:

ALTER TABLE WORKPACKAGES ADD FOREIGN KEY (EMPLOYEEID) REFERENCES EMPLOYEES (EMPLOYEEID); 

When this key is enforced, Oracle checks that all employeeid present in Workpackages table is present in Employees table.

Your options:

Find the offending keys by running

SELECT employeeid FROM   workpackages WHERE  employeeid NOT IN (SELECT employeeid                           FROM   employees);  

and then insert them into the employee table.

Another option is to use NOVALIDATE so that existing data isn't checked, but any new inserts/updates will be validated. See this fiddle for demo on this.

回答2:

The same problem puzzled me a lot when I am trying to add constraint foreign key.Now I have made it.I key in some values in the father table.For example:

alter table A add constraint A_01 foreign key (CODE) references B(CODE); I key in :insert into B(CODE) values(0); and then it works!

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