Question

使用Rails迁移（但并不重要）。我试图在这里创建一个视图，但我得到了

Mysql2::Error: View's SELECT contains a subquery in the FROM clause:
CREATE VIEW `lanciao` AS

当我尝试这个时：

create view lanciao as
  select
    subtime(payment.created_at, '0 5:0:0') as transaction_date,
    `order_item`.total_quantity,
    payment.amount as amount,
    `order`.payment_type
  from payments payment
  join orders `order` on `order`.id = payment.order_id
  left join donation_items donation on donation.order_id = `order`.id
  inner join (
    select order_id, sum(quantity) total_quantity 
    from order_items
    group by order_id
  ) `order_item` on `order`.id = `order_item`.order_id
  where payment.payment_state in ('settled', 'completed', 'captured', 'authorized', 'approved')
  and `order`.fixed_order_id is null

如果没有create view lanciao，我可以将select块运行到最后。我试图重构这个，但无法让它发挥作用。我该如何解决这个问题？

我也知道将它分成不同的观点并互相参考，但我不会喜欢这种方式。

Answer 1

MySQL docs州：

在MySQL 5.7.7之前，SELECT语句不能在FROM子句中包含子查询。

如果您可以升级到MySQL 5.7.7+，那么您应该可以完全按照自己的意愿去做。

否则，您可能想尝试创建子查询的视图，然后在FROM中使用该视图。

所以你的SQL可能看起来像：

create view subquery_view as
  select order_id, sum(quantity) total_quantity 
  from order_items
  group by order_id

create view lanciao as
  select
    subtime(payment.created_at, '0 5:0:0') as transaction_date,
    `order_item`.total_quantity,
    payment.amount as amount,
    `order`.payment_type
  from payments payment
  join orders `order` on `order`.id = payment.order_id
  left join donation_items donation on donation.order_id = `order`.id
  inner join subquery_view as `order_item` on `order`.id = `order_item`.order_id
  where payment.payment_state in ('settled', 'completed', 'captured', 'authorized', 'approved')
  and `order`.fixed_order_id is null

请注意，将视图嵌套在彼此内部可能会导致性能问题，但我不知道另一种方法。

Mysql2 ::错误：在运行rails迁移时，View的SELECT子句中包含一个子查询

1 个答案: