title: Customer ID null even though there is a sequence
body: <p>Here are my create tables and I'm using <code>INT</code> datatype for <code>Customer ID</code>, <code>Restaurant ID</code> and <code>Owner ID</code>.</p>
  <pre><code>DROP TABLE RESERVATION;
  DROP TABLE RESTAURANT;
  DROP TABLE CUSTOMER;
  DROP TABLE RESTAURANTOwner;
  
  CREATE EXTENSION IF NOT EXISTS citext;
  
  CREATE TABLE CUSTOMER 
  (
      CUSTOMER_ID INT primary key NOT NULL,
      CUSTOMER_FIRSTNAME VARCHAR(30),
      CUSTOMER_SECONDNAME VARCHAR(30),
      CUSTOMER_EMAIL CITEXT, 
      CUSTOMER_USERNAME VARCHAR(80), 
      CUSTOMER_PASSWORD VARCHAR(80), 
      CUSTOMER_PHONE VARCHAR(20),
      CUSTOMER_SALT INT NOT NULL
  );
  
  CREATE TABLE RESTAURANTOwner 
  (
      OWNER_ID INT primary key NOT NULL,
      OWNER_FIRSTNAME VARCHAR(30),
      OWNER_SECONDNAME VARCHAR(30),
      OWNER_EMAIL CITEXT, 
      OWNER_USERNAME VARCHAR(80), 
      OWNER_PASSWORD VARCHAR(80), 
      OWNER_PHONE VARCHAR(20),
      OWNER_SALT INT NOT NULL
  );
  
  CREATE TABLE RESTAURANT 
  (
      RESTAURANT_ID INT primary key NOT NULL,
      OWNER_ID INT NOT NULL,
      RESTAURANT_NAME VARCHAR(40),
      RESTAURANT_LAYOUT VARCHAR(255),
  
      CONSTRAINT FK_OWNER_ID 
          FOREIGN KEY (OWNER_ID) 
              REFERENCES RESTAURANTOwner(OWNER_ID)
  );
  
  CREATE TABLE RESERVATION 
  (
      RESTAURANT_ID INT NOT NULL,
      CUSTOMER_ID INT NOT NULL,
      RESERVATION_TIME Time,
      RESERVATION_DATE DATE,
  
      PRIMARY KEY (RESTAURANT_ID, CUSTOMER_ID, RESERVATION_TIME, RESERVATION_DATE),
      CONSTRAINT FK_CUSTOMER_ID 
          FOREIGN key (CUSTOMER_ID) 
              REFERENCES CUSTOMER(CUSTOMER_ID),
      CONSTRAINT FK_RESTAURANT_ID 
          FOREIGN KEY (RESTAURANT_ID) 
              REFERENCES RESTAURANT(RESTAURANT_ID)
  );
  </code></pre>
  <p>Here are the sequences and inserts. As you can see the sequences, they start with 1 and increment by 1, which means customer id cannot be NULL.</p>
  <pre><code>  CREATE SEQUENCE IF NOT EXISTS public.CUSTOMER_ID
              START WITH 1
              INCREMENT BY 1
              NO MINVALUE
              NO MAXVALUE
              CACHE 1;
              
    CREATE SEQUENCE IF NOT EXISTS public.OWNER_ID
              START WITH 1
              INCREMENT BY 1
              NO MINVALUE
              NO MAXVALUE
              CACHE 1;
              
    CREATE SEQUENCE IF NOT EXISTS public.RESTAURANT_ID
              START WITH 1
              INCREMENT BY 1
              NO MINVALUE
              NO MAXVALUE
              CACHE 1;
  
  INSERT INTO CUSTOMER (CUSTOMER_FIRSTNAME, CUSTOMER_SECONDNAME, CUSTOMER_EMAIL, CUSTOMER_USERNAME, CUSTOMER_PASSWORD, CUSTOMER_PHONE, CUSTOMER_SALT)
  VALUES ('Asik', 'Biho', 'testmass@gmail.com', 'mass2000', 'Passw0rd', '+4367712333213', 32131);
  INSERT INTO CUSTOMER (CUSTOMER_FIRSTNAME, CUSTOMER_SECONDNAME, CUSTOMER_EMAIL, CUSTOMER_USERNAME, CUSTOMER_PASSWORD, CUSTOMER_PHONE, CUSTOMER_SALT)
  VALUES ('Martin' , 'Mahmody', 'mahmodysecurity@lego.tr', 'mahmo00', 'MAhmoistStarK1', '+4367700992112', 32131);
  INSERT INTO CUSTOMER (CUSTOMER_FIRSTNAME, CUSTOMER_SECONDNAME, CUSTOMER_EMAIL, CUSTOMER_USERNAME, CUSTOMER_PASSWORD, CUSTOMER_PHONE, CUSTOMER_SALT)
  VALUES ('Sebastian',  'Dorner', 'Sebastian@dorner.at', 'bastian13', 'MyPasswordIsEasy', '+436993213213', 111);
  </code></pre>
  <p>So when I run it, it says that the Customer_ID is <code>NULL</code>, which shouldn't be since I have sequence which increments every time we have insert new user/customer.</p>