Question

I m 试图用 are子质问一下这块 s子:

WHERE (("participants"."accepted" =  f  AND "participants"."contact_id" = 1) 
  OR "participants"."id" IS NULL)

因此,我想 (accepted && Liaison_id=1)OR NUL



这里,我是在阿拉伯民族解放军中走过的。

participants[:accepted].eq(false).and(participants[:contact_id].eq(1).
  or(participants[:id].is(nil)


问题在于:

("participants"."accepted" =  f  AND "participants"."contact_id" = 1 OR "participants"."id" IS NULL)


请注意,我和条件周围缺乏父母。 一、导 言

accepted && (contact_id=1 OR NULL)


在AREL询问中添加母体不会影响。 任何想法?

Answer 1

我认为,根据运营商的说法,优先权

The problem is that AND has higher precedence than OR. So 1 AND 2 OR 3 is equivalent to (1 AND 2) OR 3.

作为副注:如果你使用一个像

User.where((User[:created_at] > 3.days.ago) & (User[:enabled] == true))

Answer 2

You can generate parentheses using Arel::Nodes::Grouping.

participants = Arel::Table.new("participants")

arel = participants.grouping(
  participants[:accepted].eq(false).and(participants[:contact_id].eq(1))
).or(participants[:id].eq(nil))

arel.to_sql # => (("participants"."accepted" =  f  AND "participants"."contact_id" = 1) OR "participants"."id" IS NULL)

Answer 3

Why not flip them around. Should be equivalent to:

participants[:id].is(nil).or(participants[:accepted].eq(false).and(participants[:contact_id].eq(1))

我希望,我要谈谈上文适当阐述的教区,但你看到我所说的话。

Answer 4

Here s a method that allows you to use existing AR methods such as where and perhaps any existing scopes, etc in your code. So it s easy to reuse existing AR code with Arel as needed.

class Participant
  scope :grouped, -> {
    group1 = arel_table.grouping(where(accepted: false, contact_id: 1).arel.constraints)
    group2 = arel_table.grouping(where(id: nil).arel.constraints)

    where(group1.or(group2))
  }
end

This works in Rails 7, and perhaps Rails 6.x as well.

友情链接