SELECT O.ID,O.ORDER_NUMBER,O.CUSTOMER_ID,C.ID,C.NAME
FROM ORDERS O FULL OUTER JOIN CUSTOMERS C ON C.ID=O.CUSTOMER_ID;
注意：MySQL是不支持全外的连接的，这里给出的写法适合Oracle和DB2。但是可以通过左外和右外求合集来获取全外连接的查询结果。下图是上面SQL在Oracle下执行的结果：
语句10：左外和右外的合集，实际上查询结果和语句9是相同的。
SELECT O.ID,O.ORDER_NUMBER,O.CUSTOMER_ID,C.ID,C.NAME
FROM ORDERS O LEFT OUTER JOIN CUSTOMERS C ON C.ID=O.CUSTOMER_ID
UNION
SELECT O.ID,O.ORDER_NUMBER,O.CUSTOMER_ID,C.ID,C.NAME
FROM ORDERS O RIGHT OUTER JOIN CUSTOMERS C ON C.ID=O.CUSTOMER_ID;
语句9和语句10的查询结果是相同的，如下：
四、联合连接(UNION JOIN)：这是一种很少见的连接方式。Oracle、MySQL均不支持，其作用是：找出全外连接和内连接之间差异的所有行。这在数据分析中排错中比较常用。也可以利用数据库的集合操作来实现此功能。
语句11：联合查询(UNION JOIN)例句，还没有找到能执行的SQL环境。
SELECT O.ID,O.ORDER_NUMBER,O.CUSTOMER_ID,C.ID,C.NAME
FROM ORDERS O UNION JOIN CUSTOMERS C ON C.ID=O.CUSTOMER_ID
语句12：语句11在DB2下的等价实现。还不知道DB2是否支持语句11呢!
SELECT O.ID,O.ORDER_NUMBER,O.CUSTOMER_ID,C.ID,C.NAME
FROM ORDERS O FULL OUTER JOIN CUSTOMERS C ON C.ID=O.CUSTOMER_ID
EXCEPT
SELECT O.ID,O.ORDER_NUMBER,O.CUSTOMER_ID,C.ID,C.NAME
FROM ORDERS O INNER JOIN CUSTOMERS C ON C.ID=O.CUSTOMER_ID;
语句13：语句11在Oracle下的等价实现。
SELECT O.ID,O.ORDER_NUMBER,O.CUSTOMER_ID,C.ID,C.NAME
FROM ORDERS O FULL OUTER JOIN CUSTOMERS C ON C.ID=O.CUSTOMER_ID
MINUS
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