外键刷新

Question

You will have to forgive me as its been a while since I have created a database.

I have created the following table;

CREATE TABLE Counties (
    CountID VARCHAR(10) PRIMARY KEY,
    Countyname CHAR(10)
);

Now I want to create the second one;

CREATE TABLE STAFF (
    RepID VARCHAR(10) PRIMARY KEY,
    Surname CHAR(10),
    foreign key (CountID) references Counties(CountID)
);

However I get;

CREATE TABLE STAFF (RepID VARCHAR(10) PRIMARY KEY , Surname CHAR(10),
foreign key (CountID) references Counties(CountID)) Error at Command
Line : 1 Column : 84 Error report - SQL Error: ORA-00904: "COUNTID":
invalid identifier
00904. 00000 -  "%s: invalid identifier"
*Cause:    
*Action:

I have searched around and have read it because whatever you are trying to reference doesn't exist.

However;

DESCRIBE COUNTIES;

 Name       Null      Type         
----------  --------  ------------  
COUNTID     NOT NULL  VARCHAR2(10)  
COUNTYNAME            CHAR(10)

Answer 1

You have to specify the field first. Now you are creating just the FK on a field that does not exist. The statement should define the field, and define the foreign key separately:

CREATE TABLE STAFF (
  RepID VARCHAR(10) PRIMARY KEY , 
  Surname CHAR(10), 
  CountID VARCHAR(10),
  foreign key (CountID) references Counties(CountID));

There is a short syntax that lets you combine them. But it is slightly different and it actually adds the FK to the field declaration (thanks to ypercube). It still needs the field type, but lets you add a shortened FK declaration after the field declaration:

CREATE TABLE STAFF (
  RepID VARCHAR(10) PRIMARY KEY , 
  Surname CHAR(10), 
  CountID VARCHAR(10) references Counties(CountID));