无法在 ORACLE 中启用外键 SQL

Question

所以我有一个禁用的外键（table 员工中的Manager_ID）并且我想启用它，但是我得到这个错误：

ORA-02298: cannot validate (my_username.EMP_MANAGER_FK) - parent keys not found

这是代码：

ALTER TABLE Employees ENABLE CONSTRAINT EMP_MANAGER_FK;

table 的创建方式如下：

 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(2,2), 
    "MANAGER_ID" NUMBER(6,0), 
    "DEPARTMENT_ID" NUMBER(4,0), 
    "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")
/

Answer 1

从外键的角度来看，列中的值无效。

假设您有一个 self-referencing 外键，例如：

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

然后报错提示有manager_id在employee_id列中不存在。您可以使用如下查询显示有问题的行：

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

您需要解决这个问题才能启用外键。

Answer 2

如果你想以任何方式插入数据，你可以禁用约束 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 表示检查新行或修改行的约束，但现有数据可能违反约束。

无法在 ORACLE 中启用外键 SQL

Can't enable a foreign key in ORACLE SQL

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constraints

foreign-keys

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