无法在ORACLE SQL中启用外键

问题描述

所以我有一个禁用的外键（表Employees中的Manager_ID），我想启用它，但出现此错误：

ORA-02298：无法验证（my_username.EMP_MANAGER_FK）-找不到父密钥

这是代码：

ALTER TABLE Employees ENABLE CONSTRAINT EMP_MANAGER_FK;

这是创建表的方式：

 CREATE TABLE  "EMPLOYEES" 
   (    "EMPLOYEE_ID" NUMBER(6,0),"FirsT_NAME" VARCHAR2(20),"LAST_NAME" VARCHAR2(25) CONSTRAINT "EMP_LAST_NAME_NN" NOT NULL ENABLE,"EMAIL" VARCHAR2(25) CONSTRAINT "EMP_EMAIL_NN" NOT NULL ENABLE,"PHONE_NUMBER" VARCHAR2(20),"HIRE_DATE" DATE CONSTRAINT "EMP_HIRE_DATE_NN" NOT NULL ENABLE,"JOB_ID" VARCHAR2(10) CONSTRAINT "EMP_JOB_NN" NOT NULL ENABLE,"SALARY" NUMBER(8,2),"COMMISSION_PCT" NUMBER(2,"MANAGER_ID" NUMBER(6,"DEPARTMENT_ID" NUMBER(4,"BONUS" VARCHAR2(5),CONSTRAINT "EMP_SALARY_MIN" CHECK (salary > 0) ENABLE,CONSTRAINT "EMP_ID_PK" PRIMARY KEY ("EMPLOYEE_ID")
   USING INDEX  ENABLE,CONSTRAINT "EMP_EMAIL_UK" UNIQUE ("EMAIL")
   USING INDEX  ENABLE
    )
   /
   ALTER TABLE  "EMPLOYEES" ADD CONSTRAINT "EMP_DEPT_FK" FOREIGN KEY 
    ("DEPARTMENT_ID")
      REFERENCES  "DEPARTMENTS" ("DEPARTMENT_ID") ENABLE
    /
ALTER TABLE  "EMPLOYEES" ADD CONSTRAINT "EMP_JOB_FK" FOREIGN KEY ("JOB_ID")
      REFERENCES  "JOBS" ("JOB_ID") ENABLE
/
ALTER TABLE  "EMPLOYEES" ADD CONSTRAINT "EMP_MANAGER_FK" FOREIGN KEY ("MANAGER_ID")
      REFERENCES  "EMPLOYEES" ("EMPLOYEE_ID") disABLE
/

CREATE INDEX  "EMP_DEPARTMENT_IX" ON  "EMPLOYEES" ("DEPARTMENT_ID")
/

CREATE INDEX  "EMP_JOB_IX" ON  "EMPLOYEES" ("JOB_ID")
/

CREATE INDEX  "EMP_MANAGER_IX" ON  "EMPLOYEES" ("MANAGER_ID")
/

CREATE INDEX  "EMP_NAME_IX" ON  "EMPLOYEES" ("LAST_NAME","FirsT_NAME")
/

解决方法

从外键的角度来看，列中的值无效。

假设您具有一个自引用外键，例如：

create table employees (
    employee_id int primary key,manager_id  int references employees(employee_id)
);

然后，错误消息表明manager_id列中不存在employee_id个。您可以使用以下查询来显示有问题的行：

select manager_id
from employees e
where not exists (select 1 from employees e1 where e1.employee_id = e.manager_id)

您需要先解决此问题，然后才能启用外键。

,

如果您想以任何方式插入数据，则可以禁用约束EMP_MANAGER_FK并使用 NOVALIDATE 关键字启用它。

ALTER TABLE EMPLOYEES MODIFY CONSTRAINT EMP_MANAGER_FK ENABLE NOVALIDATE;

ENABLE NOVALIDATE意味着检查了约束是否有新行或修改过的行，但是现有数据可能违反了该约束。