Mysql问题：是否有类似IN ALL的查询？

Question

例如这个查询：

SELECT `variants`.* 
  FROM `variants` INNER JOIN `variant_attributes` 
    ON variant_attributes.variant_id = variants.id 
 WHERE (variant_attributes.id IN ('2','5'))

并且变体has_many variant_attributes

我真正想要做的是找到哪个变体具有ID = 2和5的BOTH变体属性。这可能与MySQL有关吗？ Bonus Question，有没有一种快速方法可以使用Ruby on Rails，也许使用SearchLogic？

解

感谢Quassnoi提供的查询，完美无缺。

要在Rails上使用，我使用下面的named_scope，我认为这对于初学者来说更容易理解。

基本上，named_scope将返回{：from => x，：conditions => y}，上面的行用于设置y变量。

  named_scope :with_variant_attribute_values, lambda { |values|
    conditions = ["(
            SELECT  COUNT(*)
            FROM    `variant_attributes`
            WHERE   variant_attributes.variant_id = variants.id
                    AND variant_attributes.value IN (#{values.collect { |value| "?" }.join ", "})
            ) = ?
    "]
    conditions = conditions + values + [values.length]
    {
    :from => 'variants', 
    :conditions => conditions
  }}

Answer 1

假设variant_attributes (variant_id, id)是唯一的：

SELECT  `variants`.*
FROM    `variants`
WHERE   (
        SELECT  COUNT(*)
        FROM    `variant_attributes`
        WHERE   variant_attributes.variant_id = variants.id
                AND variant_attributes.id IN ('2','5')
        ) = 2

Answer 2

Quassnoi发布了你想做的mysql查询。 这是一个Variant模型的方法，它将完成等价的操作。 我正在做两种方法，一种方法，如果variant_attributes (variant_id, id)是唯一的组合，一种方法如果它们不是

独特：

class Variant < ActiveRecord::Base
  has_many :variant_attributes
  named_scope :with_variant_attributes, lamda { |*ids|
     ids = ids.flatten
     if(ids.length>0)
       result = {:include => :variant_attributes}
       sql_params = {:length => ids.length,:ids => ids}
       result[:conditions] = ["(:length = (select count(*) from variant_attributes
                                          where id in (:ids))",sql_params]
       result
     else
       nil
     end
   }
end

非独特

class Variant < ActiveRecord::Base
  has_many :variant_attributes
  named_scope :with_variant_attributes, lamda { |*ids|
     ids = ids.flatten
     if(ids.length>0)
       result = {:include => :variant_attributes}
       conditions = []
       sql_params = {}

       ids.each_with_index do |id,i|
         conditions << "( 1 = Select Count(*) from variant_attributes where id = :id#{i})"
         sql_params["id#{i}"] =  id
       end
       result[:conditions] = [ '(' + conditions.join(' AND ') + ')', sql_params]
       result
     else
       nil
     end
   }
end

可以通过以下方式使用：

# Returns all Variants with variant_attributes 1, 2, & 3
vars = Variant.with_variant_attributes(1,2,3) 

# Returns Variant 5 if it has attributes 3 & 5, or null if it doesn't
vars = Variant.with_variant_attributes(3,5).find_by_id(5)

#Returns Variants between 1 and 20 if that have an attribute of 2
vars = Variant.with_variant_attributes(2).find(:conditions => "id between 1 and 20")

#can accept a variable array of ids
my_ids = [3,5]
vars = Variant.with_variant_attributes(my_ids)

此代码尚未经过测试。

Answer 3

我会为此创建一个named_scope：

class Variant < ActiveRecord::Base
  has_many    :variant_attributes

  named_scope :with_variant_attributes, lambda { |*ids| { 
            :joins => :variant_attributes, 
            :conditions => {:variant_attributes=>{:id=>ids}},
            :group => "variants.id",
            :having => "count(variants.id) = #{ids.size}"
            }
          }
end

现在您可以使用命名范围，如下所示：

Variant.with_variant_attributes(1,2)
Variant.with_variant_attributes(1,2,3,4)

Answer 4

感谢Quassnoi提供的查询，完美无缺。

要在Rails上使用，我使用下面的named_scope，我认为这对于初学者来说更容易理解。

基本上，named_scope将返回{：from => x，：conditions => y}，上面的行用于设置y变量。

  named_scope :with_variant_attribute_values, lambda { |values|
    conditions = ["(
            SELECT  COUNT(*)
            FROM    `variant_attributes`
            WHERE   variant_attributes.variant_id = variants.id
                    AND variant_attributes.value IN (#{values.collect { |value| "?" }.join ", "})
            ) = ?
    "]
    conditions = conditions + values + [values.length]
    {
    :from => 'variants', 
    :conditions => conditions
  }}