Rails where 条件使用 NOT NIL [英] Rails where condition using NOT NIL

问题描述

使用 rails 3 样式我将如何写相反的内容:

Using the rails 3 style how would I write the opposite of:

Foo.includes(:bar).where(:bars=>{:id=>nil})

我想找到 id 不是 nil 的地方.我试过了:

I want to find where id is NOT nil. I tried:

Foo.includes(:bar).where(:bars=>{:id=>!nil}).to_sql

但这会返回:

=> "SELECT     \"foos\".* FROM       \"foos\"  WHERE  (\"bars\".\"id\" = 1)"

这绝对不是我需要的，而且几乎看起来像是 ARel 中的一个错误.

That's definitely not what I need, and almost seems like a bug in ARel.

推荐答案

Rails 3 的规范方法:

The canonical way to do this with Rails 3:

Foo.includes(:bar).where("bars.id IS NOT NULL")

ActiveRecord 4.0 及更高版本添加了 where.not 所以你可以这样做:

ActiveRecord 4.0 and above adds where.not so you can do this:

Foo.includes(:bar).where.not('bars.id' => nil)
Foo.includes(:bar).where.not(bars: { id: nil })

处理表之间的范围时，我更喜欢利用 merge 以便我可以更轻松地使用现有范围.

When working with scopes between tables, I prefer to leverage merge so that I can use existing scopes more easily.

Foo.includes(:bar).merge(Bar.where.not(id: nil))

此外，由于 includes 并不总是选择连接策略，您应该使用 references 也在这里，否则你可能会得到无效的 SQL.

Also, since includes does not always choose a join strategy, you should use references here as well, otherwise you may end up with invalid SQL.

Foo.includes(:bar)
   .references(:bar)
   .merge(Bar.where.not(id: nil))

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