Question

假设我的客户有很多付款。如何查询以获取过去90天内没有付款记录的所有客户？

clients
=======
id          integer
name        string

payments
========
id          integer
client_id   integer
created_at  datetime

基本上是反过来：

select *
from clients
inner join payments on payments.client_id = clients.id
where payments.created_at > utc_timestamp() - interval 90 day

希望比以下更有效率：

select *
from clients 
where id not in (
  select *
  from clients
  inner join payments on payments.client_id = clients.id
  where payments.created_at > utc_timestamp() - interval 90 day
)

Answer 1

确保payments(client_id)上有索引，甚至更好，payments(client_id, created_at）。

有关编写查询的替代方法，您可以尝试not exists，例如：

select  *
from    clients c
where   not exists
        (
        select  *
        from    payments p
        where   p.payments.client_id = clients.id
                and payments.created_at > utc_timestamp() - interval 90 day
        )

或专属左连接：

select  *
from    clients c
left join
        payments p
on      p.payments.client_id = clients.id
        and payments.created_at > utc_timestamp() - interval 90 day
where   p.client_id is null

如果两者都很慢，请在问题中添加explain extended输出，以便我们了解原因。

Answer 2

select *
from clients
left join payments on 
    payments.client_id = clients.id and 
    payments.created_at > utc_timestamp() - interval 90 day
where payments.client_id is null

SQL查询：过去90天内没有付款

2 个答案: