如何在Presto SQL中左联接

Question

即使在阅读了文档之后，我也无法在Presto中找到一个简单的左联接。我非常熟悉Postgres，并在那里测试了我的查询，以确保我没有明显的错误。请参考以下代码：

select * from
(select cast(order_date as date),   
count(distinct(source_order_id)) as prim_orders, 
sum(quantity) as prim_tickets, 
sum(sale_amount) as prim_revenue 
from table_a
where order_date >= date '2018-01-01'
group by 1)
left join
(select summary_date, 
sum(impressions) as sem_impressions, 
sum(clicks) as sem_clicks, 
sum(spend) as sem_spend,  
sum(total_orders) as sem_orders, 
sum(total_tickets) as sem_tickets, 
sum(total_revenue) as sem_revenue 
from table_b
where site like '%SEM%'
and summary_date >= date '2018-01-01'
group by 1) as b
on a.order_date = b.summary_date

运行时出现以下错误

SQL Error: Failed to run query
Failed to run query
line 1:1: mismatched input 'on' expecting {'(', 'SELECT', 'DESC', 'WITH', 
'VALUES', 'CREATE', 'TABLE', 'INSERT', 'DELETE', 'DESCRIBE', 'GRANT', 
'REVOKE', 'EXPLAIN', 'SHOW', 'USE', 'DROP', 'ALTER', 'SET', 'RESET', 'START', 'COMMIT', 'ROLLBACK', 'CALL', 'PREPARE', 'DEALLOCATE', 'EXECUTE'} (Service: AmazonAthena; Status Code: 400; Error Code: InvalidRequestException; Request ID: a33a6671-07a2-4d7b-bb75-f70f7b82409e)
line 1:1: mismatched input 'on' expecting {'(', 'SELECT', 'DESC', 'WITH', 'VALUES', 'CREATE', 'TABLE', 'INSERT', 'DELETE', 'DESCRIBE', 'GRANT', 'REVOKE', 'EXPLAIN', 'SHOW', 'USE', 'DROP', 'ALTER', 'SET', 'RESET', 'START', 'COMMIT', 'ROLLBACK', 'CALL', 'PREPARE', 'DEALLOCATE', 'EXECUTE'} (Service: AmazonAthena; Status Code: 400; Error Code: InvalidRequestException; Request ID: a33a6671-07a2-4d7b-bb75-f70f7b82409e)

Answer 1

我注意到的第一个问题是，联接子句假设第一个子查询别名为a，但它根本没有别名。我建议对该表进行别名处理，看看是否可以修复它(我还建议在cast()语句之外显式地对order_date列进行别名，因为您是在该列上加入的(。

试试这个：

select * from
(select cast(order_date as date) as order_date,   
count(distinct(source_order_id)) as prim_orders, 
sum(quantity) as prim_tickets, 
sum(sale_amount) as prim_revenue 
from table_a
where order_date >= date '2018-01-01'
group by 1) as a
left join
(select summary_date, 
sum(impressions) as sem_impressions, 
sum(clicks) as sem_clicks, 
sum(spend) as sem_spend,  
sum(total_orders) as sem_orders, 
sum(total_tickets) as sem_tickets, 
sum(total_revenue) as sem_revenue 
from table_b
where site like '%SEM%'
and summary_date >= date '2018-01-01'
group by 1) as b
on a.order_date = b.summary_date

Answer 2

一个选项是使用with:声明子查询

with a as 
(select cast(order_date as date),   
count(distinct(source_order_id)) as prim_orders, 
sum(quantity) as prim_tickets, 
sum(sale_amount) as prim_revenue 
from table_a
where order_date >= date '2018-01-01'
group by 1),
b as 
(select summary_date, 
sum(impressions) as sem_impressions, 
sum(clicks) as sem_clicks, 
sum(spend) as sem_spend,  
sum(total_orders) as sem_orders, 
sum(total_tickets) as sem_tickets, 
sum(total_revenue) as sem_revenue 
from table_b
where site like '%SEM%'
and summary_date >= date '2018-01-01'
group by 1)
select * from a
left join b
on a.order_date = b.summary_date;