sql - error ORA-02270: no matching unique or primary key for this column-list -

I am practicing a laboratory manual practice in which I have to make 6 tables, 5 is successful.

But there is a line error

  constraint GRADE_Designation_FK foreign key (designation) references employee (designation),  

Error 7 :

ORA-02270: this column lists a match unique or primary key

2 linked tables of queries made

  table staff (Empno number (4) constraint EMPLOYEE_Empno_PK primary key, name varchar2 (10) nOT nULL, title varchar2 (50), qualifying varchar2 (10), Joindate date); Table grades (designation varchar2 (50) barrier GRADE_Designation_PK primary key, grades Number (2), TotalPosts number (4), PostsAvailable number (4), grades between barrier GRADE_Grade_CK probes (1 and 20), barrier GRADE_PostsAvailable_CK Czech (PostsAvailable to & Create lt; = total posts), barrier GRADE_Designation_FK foreign key (designation) reference employee (designation));  

Try out

  table grade (make designation varchar2 (50) barrier GRADE_Designation_PK primary key, grades Number (2), TotalPosts number (4), PostsAvailable Number (4), Handicap GRADE_Grade_CK check (between grades 1 and 20), hindered GRADE_PostsAvailable_CK check (post available & lieutenant; = total posts); Table Create EMPLOYEE (Mpno number (4) constraint EMPLOYEE_Empno_PK primary key, name varchar2 (10) NOT NULL, title varchar2 (50) unique unique ability varchar2 (10), Joindate date default sysdate barrier EMPLOYEE_Designation_FK foreign key (designation) reference GRADE (Designation),);  

Now the new error

barrier EMPLOYEE_Designation_FK foreign key (designation) reference grade (designation) on line 8 *

Error: < / P>

ORA-02253: barrier specification is not allowed

'They impede the wrong table. You should make a foreign key on EMPLOYEE.DISIGNATION, referencing back to GRADE.Designation.

If your table is something that should look:

  table to make GRADE (designation varchar2 (50) barrier GRADE_Designation_PK primary key, grades Number (2), TotalPosts number (4) , PostsAvailable number (4), barrier grade between GRADE_Grade_CK probes (1 and 20), barrier GRADE_PostsAvailable_CK Czech (PostsAvailable & lt; = TotalPosts),); CREATE TABLE employees (Empno number (4) constraint EMPLOYEE_Empno_PK primary key, name varchar2 (10) NOT NULL, title varchar2 (50) barrier EMPLOYEE_FK1 reference grade (designation), qualifying varchar2 (10), Joindate date);  

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