我需要FULL OUTER JOIN多个表.我知道如何从

here开始加入两个表.但我有几个表,我不能将它们应用于它们.我怎样才能实现它？

我的SQL代码,如下：

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

我也尝试了这个查询：

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

上次查询执行时间很长,我需要更快的查询.

最佳答案 我想在3个表上有一个FULL OUTER JOIN,你需要这样做：

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

我建议你创建一些临时表,如t1,t2和t3,用于存储查询结果,然后使用上面的查询.