我需要full outer join多個表.我知道如何從
here開始加入兩個表.但我有幾個表,我不能將它們應用於它們.我怎樣才能實現它？
我的sql**,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
我也嘗試了這個查詢：
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
上次查詢執行時間很長,我需要更快的查詢.
最佳答案 我想在3個表上有乙個full outer join,你需要這樣做：
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
作為替代方案：
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
我建議你建立一些臨時表,如t1,t2和t3,用於儲存查詢結果,然後使用上面的查詢.
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