title: Adding a foreign key to existing table
body: <p>I have been trying to add these keys to my table but I get an error</p>
  
  <blockquote>
    <p>ORA-01735: invalid ALTER TABLE option</p>
  </blockquote>
  
  <p>My code:</p>
  
  <pre><code>ALTER TABLE Room
  ADD FOREIGN KEY (RoomType_ID) REFERENCES RoomType(RoomType_ID), 
  ADD FOREIGN KEY (Reservation_ID) REFERENCES Reservation(Reservation_ID), 
  ADD FOREIGN KEY (Gust_ID) REFERENCES Gust(Gust_ID);
  </code></pre>
  
  <p>Tables</p>
  
  <pre><code>CREATE TABLE Gust ( Gust_ID INT NOT NULL PRIMARY KEY, First_Name VARCHAR(50), Last_Name VARCHAR(50), Email VARCHAR(20), phone_number INT(10), Address VARCHAR(30) )
  
  CREATE TABLE Reservation ( Reservation_ID INT NOT NULL PRIMARY KEY, Start_Date Date, End_Date Date )
  
  CREATE TABLE Room ( Room_ID INT NOT NULL PRIMARY KEY, Price INT )
  
  CREATE TABLE RoomType ( RoomType_ID INT NOT NULL PRIMARY KEY, Class VARCHAR(10), ExtraPrice INT )
  </code></pre>