|  |  |  | Libgnomedb Reference Manual |  | 
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The database structure is described in the next paragraphs (in PostgreSQL's syntax in this example):
The 'id' field is the primary key of this table.
      CREATE TABLE customers (
      id serial NOT NULL,
      name character varying(35) NOT NULL,
      default_served_by integer,
      country character varying(20),
      city character varying(30)
      );
    Each row in the table represents an order passed by a customer. The customer is identified through a foreign key (the 'customer' field). The 'id' field is the primary key of this table.
      CREATE TABLE orders (
      id serial NOT NULL,
      customer integer NOT NULL,
      creation_date date DEFAULT now() NOT NULL,
      delivery_before date,
      delivery_date date
      );
    Each row in the table represents an item in an order. The referenced order is identified through a foreign key (the 'order_id' field); the referenced item is identified through the 'product_ref' foreign key. This table has no primary key.
      CREATE TABLE order_contents (
      order_id integer NOT NULL,
      product_ref character varying(15) NOT NULL,
      quantity integer DEFAULT 1 NOT NULL,
      discount double precision DEFAULT 0 NOT NULL
      );
    | << A small example | Coding the application >> |