It is recommended that you create SQL scripts that will create your tables for you in Oracle.  Here's how to do it:

1. Create a file with the extension .sql to denote that it contains SQL statements to be executed.  Example:  tables.sql

2. In this file, put the SQL statements needed to create this table.  You may also choose to populate this table.

    Example:

DROP TABLE XCUSTOMERS;

CREATE TABLE XCUSTOMERS (
    CUSTNO     NUMBER(9)  NOT NULL PRIMARY KEY,
    CUSTNAME   CHAR(20),
    CUSTCITY   CHAR(20));
 

INSERT INTO XCUSTOMERS  VALUES(1000,'Guy, Buddy','Chicago');
INSERT INTO XCUSTOMERS  VALUES(1001,'Rush, Otis','Chicago');
INSERT INTO XCUSTOMERS  VALUES(1002,'Clapton, Eric','London');
INSERT INTO XCUSTOMERS  VALUES(1003,'Green, Peter','London');
INSERT INTO XCUSTOMERS  VALUES(1004,'Bloomfield, Mike','Chicago');
INSERT INTO XCUSTOMERS  VALUES(1005,'King, Freddie','Dallas');
INSERT INTO XCUSTOMERS  VALUES(1006,'King, B.B.','Memphis');
 

3.  After saving the file, run SQLPlus by typing the following at the prompt:

        sqlplus /

4. At the SQL prompt, run the script by typing the name of the script preceeded by the `@` sign:

        SQL> @smp.sql

5.  You should see your table being created/populated.  To check, do a select on the table:

SQL> select * from xcustomers;

    CUSTNO CUSTNAME             CUSTCITY
---------- -------------------- --------------------
      1000 Guy, Buddy           Chicago
      1001 Rush, Otis           Chicago
      1002 Clapton, Eric        London
      1003 Green, Peter         London
      1004 Bloomfield, Mike     Chicago
      1005 King, Freddie        Dallas
      1006 King, B.B.           Memphis

7 rows selected.

SQL>
 

6.  There have been questions on how to reference foreign keys.  The following examples illustrate how.

CREATE TABLE emp
          (empno NUMBER PRIMARY KEY,
           ename VARCHAR2(10) NOT NULL,
           job VARCHAR2(9),
           mgr NUMBER REFERENCES emp(empno),
           hiredate DATE,
           deptno NUMBER(2) NOT NULL,
           FOREIGN KEY deptno REFERENCES dept(deptno));

mgr is a foriegn key to the same table
deptno is a foriegn key to the dept table

You can reference foreign keys in two ways: 1) after defining the attribute (as in the case of manager's employee number), or 2) after all attributes have been defined (as in the department number).