如何在MySQL中完全外部连接多个表

我需要

完全外部联接

多个表。我知道如何从中

完全外部联接两个表。但是我有好几张桌子，我不能把它用在上面。我怎样才能实现它？

我的SQL代码，如下所示：

INSERT INTO table
(
  customer_id
 ,g01
 ,g02
 ,g03
 ,has_card
 ,activity
  )
  SELECT sgd.customer_id, sgd.g01,sgd.g02,sgd.g03,sc.value, a.activity
  FROM s_geo_data sgd
  LEFT JOIN s_category sc
  ON sc.customer_id = sgd.customer_id
    UNION
  SELECT sgd.customer_id, sgd.g01,sgd.g02,sgd.g03,sc.value, a.activity
  FROM s_geo_data sgd
  RIGHT JOIN s_category sc
  ON sc.customer_id = sgd.customer_id

    UNION

  SELECT sgd.customer_id, sgd.g01,sgd.g02,sgd.g03,sc.value, a.activity
  FROM s_geo_data sgd
  LEFT JOIN s_activity a
  ON a.customer_id = sgd.customer_id
    UNION
  SELECT sgd.customer_id, sgd.g01,sgd.g02,sgd.g03,sc.value, a.activity
  FROM s_geo_data sgd
  RIGHT JOIN s_activity a
  ON a.customer_id = sgd.customer_id

我还尝试了这个查询：

INSERT INTO reportls.table
(
  customer_id
 ,g01
 ,g02
 ,g03
 ,has_card
 ,activity
  )
  SELECT sgd.customer_id, sgd.g01,sgd.g02,sgd.g03,sc.value, a.activity
  FROM s_geo_data sgd
  LEFT JOIN s_category sc
  ON sc.customer_id = sgd.customer_id
  LEFT JOIN s_activity a
  ON sc.customer_id = sgd.customer_id

    UNION

  SELECT sgd.customer_id, sgd.g01,sgd.g02,sgd.g03,sc.value, a.activity
  FROM s_geo_data sgd
  LEFT JOIN s_category sc
  ON sc.customer_id = sgd.customer_id
  RIGHT JOIN s_activity a
  ON a.customer_id = sgd.customer_id

    UNION

  SELECT sgd.customer_id, sgd.g01,sgd.g02,sgd.g03,sc.value, a.activity
  FROM s_geo_data sgd
  RIGHT JOIN s_category sc
  ON sc.customer_id = sgd.customer_id
  LEFT JOIN s_activity a
  ON a.customer_id = sgd.customer_id

最后一个查询执行很长时间，我需要更快的查询
 我认为要对3个表进行
完全外部联接
，您需要这样做：

SELECT t1.value, t2.value, t3.value
FROM t1 LEFT JOIN t2 ON t1.value = t2.value
        LEFT JOIN t3 ON t1.value = t3.value
UNION ALL
SELECT t1.value, t2.value, t3.value
FROM t2 LEFT JOIN t1 ON t1.value = t2.value
        LEFT JOIN t3 ON t2.value = t3.value
WHERE t1.value IS NULL
UNION ALL
SELECT t1.value, t2.value, t3.value
FROM t3 LEFT JOIN t1 ON t1.value = t3.value
        LEFT JOIN t2 ON t2.value = t3.value
WHERE t1.value IS NULL AND t2.value IS NULL

作为替代方案：

SELECT t1.value, t2.value, t3.value
FROM t1 FULL OUTER JOIN t2 ON t1.value = t2.value
        FULL OUTER JOIN t3 ON t1.value = t3.value


我建议您创建一些临时表，如
t1
、
t2
和
t3
来存储查询结果，然后在这些表上使用上述查询。
我执行查询，等待20分钟，然后按取消。）@20分钟真的很高，但我想不出更好的查询；）@谢谢你的回复！！为什么要编写UNION ALL not UNION？对于完整的外部联接
n
表，这个比例如何？