对两个表的简单外连接

下列查询使用与前面示例相同的 Projection 子句、表和比较条件，但这一次它用 GBase 8s 扩展语法创建简单外连接。

图: 查询

SELECT c.customer_num, c.lname, c.company, 
          c.phone, u.call_dtime, u.call_descr
          FROM customer c, OUTER cust_calls u
          WHERE c.customer_num = u.customer_num;

cust_calls 表前面的附加关键字 OUTER 使该表成为从属表。外连接导致查询返回有关所有客户的信，而不管它们是否已致电客户服务中心。检索控制表 customer 的所有行，并且将 NULL 值指定给从属表 cust_calls 的列，如下所示。

图: 查询结果

customer_num  101
          lname         Pauli
          company       All Sports Supplies
          phone         408-789-8075
          call_dtime    
          call_descr    
          
          customer_num  102
          lname         Sadler
          company       Sports Spot
          phone         415-822-1289
          call_dtime    
          call_descr    
          ⋮
          customer_num  107
          lname         Ream
          company       Athletic Supplies
          phone         415-356-9876
          call_dtime    
          call_descr    
          
          customer_num  108
          lname         Quinn
          company       Quinn's Sports
          phone         415-544-8729
          call_dtime    
          call_descr