Question

我正在练习实验手册练习，我必须在其中创建6个表格。创造5是成功的。

但有一行是错误

constraint GRADE_Designation_FK 
   FOREIGN KEY(Designation) References EMPLOYEE(Designation),

第7行的错误：

ORA-02270：此列列表没有匹配的唯一键或主键

2个链接表的查询是

create table EMPLOYEE
(
    Empno number(4) constraint EMPLOYEE_Empno_PK PRIMARY KEY,
    Name varchar2(10) not null,
    Designation varchar2(50),
    Qualification varchar2(10),
    Joindate date
);

create table GRADE
(
    Designation varchar2(50) constraint GRADE_Designation_PK PRIMARY KEY,
    Grade number(2),
    TotalPosts number(4),
    PostsAvailable number(4),

    constraint GRADE_Grade_CK  check(Grade between 1 and 20),
    constraint GRADE_PostsAvailable_CK check(PostsAvailable <= TotalPosts),
    constraint GRADE_Designation_FK FOREIGN KEY(Designation) References EMPLOYEE(Designation)
);

尝试

create table GRADE
(
    Designation varchar2(50) constraint GRADE_Designation_PK PRIMARY KEY,
    Grade number(2),
    TotalPosts number(4),
    PostsAvailable number(4),

    constraint GRADE_Grade_CK  check(Grade between 1 and 20),
    constraint GRADE_PostsAvailable_CK check(PostsAvailable <= TotalPosts)
);

create table EMPLOYEE
(
    Empno number(4) constraint EMPLOYEE_Empno_PK PRIMARY KEY,
    Name varchar2(10) not null,
    Designation varchar2(50) NOT NULL UNIQUE,
    Qualification varchar2(10),
    Joindate date default sysdate

    constraint EMPLOYEE_Designation_FK FOREIGN KEY(Designation) References GRADE(Designation),
);

现在出现新错误

约束EMPLOYEE_Designation_FK FOREIGN KEY（名称）参考文献GRADE（指定）      *

第8行的错误：

ORA-02253：此处不允许约束规范

Answer 1

你在错误的桌子上得到了约束。您应该在EMPLOYEE.DESIGNATION上创建一个外键，引用回GRADE.DESIGNATION。

所以你的表应该是这样的：

create table GRADE
(
Designation varchar2(50) constraint GRADE_Designation_PK PRIMARY KEY,
Grade number(2),
TotalPosts number(4),
PostsAvailable number(4),
constraint GRADE_Grade_CK  check(Grade between 1 and 20),
constraint GRADE_PostsAvailable_CK check(PostsAvailable <= TotalPosts),
);

create table EMPLOYEE
(
Empno number(4) constraint EMPLOYEE_Empno_PK PRIMARY KEY,
Name varchar2(10) not null,
Designation varchar2(50)
  constraint EMPLOYEE_FK1
    REFERENCES GRADE(DESIGNATION),
Qualification varchar2(10),
Joindate date
);

分享并享受。

Answer 2

ORA-02270：此列列表没有匹配的唯一键或主键

这个错误非常自我解释，并告诉你错误。在您的情况下，您尝试在非主键列上创建外键，因此错误

constraint GRADE_Designation_FK FOREIGN KEY(Designation) 
               References EMPLOYEE(Designation)
                                  <--Here

Designation表中的

EMPLOYEE不是主键，您无法在非主键列上创建FK。你的表创建应该看起来像

create table GRADE
(
Designation varchar2(50) constraint GRADE_Designation_PK PRIMARY KEY,
employee_Empno number(4),
Grade number(2),
TotalPosts number(4),
PostsAvailable number(4),
constraint GRADE_Grade_CK  check(Grade between 1 and 20),
constraint GRADE_PostsAvailable_CK check(PostsAvailable <= TotalPosts),
constraint GRADE_Designation_FK FOREIGN KEY(employee_Empno) 
References EMPLOYEE(Empno));

Answer 3

执行的顺序导致了我们这个问题，确保在添加这些约束之前创建了使用NOT NULL启用的表以避免此错误。

错误ORA-02270：此列列表没有匹配的唯一键或主键

3 个答案: