从订单表中选择计数和总和，以及从事件表中选择计数和总和，其中order_id匹配和事件=到期

Question

我有两个表，一个包含订单信息，另一个包含订购事件信息，示例结构如下：

订单表：

金额2021-07-01//tr>2021-07-20

merchant_id	order_id	订单日期
1111111	23456	100
1111111	789012	50
1111111	642443	75	2021-08-12

将event上的条件添加到联接(而不是where(：

select o.merchant_id, extract(month from o.order_date) as order_month, count(o.order_id) as order_count, sum(o.order_amount) as order_sum, count(e.order_id) as expiry_count, sum(e.amount) as expiry_sum
from orders o
left join events e on e.order_id = o.order_id
and e.event = 'EXPIRY'
where o.merchant_id = '111111'
and o.order_date >= '2021-07-01'
group by o.merchant_id, order_month
order by o.merchant_id, order_month

如果在where子句中对外部联接表设置条件，则强制联接表现为内部联接(就像删除了left关键字一样(。