Question

我们有：

class Campaign::Item < ActiveRecord::Base
  belongs_to :campaign

  has_many :criteria
end

class Campaign::Item::Criterium < ActiveRecord::Base
  belongs_to :campaign_item

  # This model has a +type+ field.
end

class Campaign::Item::Criterium::Gender < Campaign::Item::Criterium
  belongs_to :campaign_item

  # This model uses the a +gender+ field.
end

class Campaign::Item::Criterium::Age < Campaign::Item::Criterium
  belongs_to :campaign_item

  # This model uses the +age_min+ and +age_max+ fields.
end

class User
  # This model has a +gender+ and +birth_date+ field.
end

如您所见，用户可以使用其中的项目制作广告系列。每个广告系列项目都可以根据性别和年龄制定许多条件。

现在我们正在尝试列出与当前用户信息匹配的所有广告系列项目。

例如：
当前用户为female并且25 years old 此用户应该能够看到只有female Gender标准的项目它还应该能够看到具有female Gender标准和Age between 18 and 30 years old标准的项目。
但是，此用户不应该看到具有female Gender标准和Age between 30 and 35 years old标准的项目。

因此，此处的目标是返回所有Campaign::Item，其中 all 的条件与当前用户的信息相匹配。目前，我们只设法返回Campaign::Item，其中至少一个标准与当前用户的信息相匹配。

以下是我们尝试实现此目标的一些查询示例：

SELECT "campaign_items".*
FROM "campaign_items"
INNER JOIN "campaign_item_criteria"
  ON "campaign_item_criteria"."campaign_item_id" = "campaign_items"."id"
WHERE
  ("campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Gender'
   AND ("campaign_item_criteria"."gender" IS NULL
        OR "campaign_item_criteria"."gender" = 'female'))
  AND ("campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Age'
       AND ("campaign_item_criteria"."age_min" IS NULL
            OR "campaign_item_criteria"."age_min" <= 17)
       AND ("campaign_item_criteria"."age_max" IS NULL
            OR "campaign_item_criteria"."age_max" >= 17))

这个不起作用，因为它试图找到同时具有Campaign::Item::Criterium::Gender和Campaign::Item::Criterium::Age类型的标准，显然，这不会很快就会出现这种情况。

SELECT "campaign_items".*
FROM "campaign_items"
INNER JOIN "campaign_item_criteria"
  ON "campaign_item_criteria"."campaign_item_id" = "campaign_items"."id"
WHERE
CASE
  WHEN "campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Gender'
       AND "campaign_item_criteria"."gender" = 'female'
       THEN 1
  WHEN "campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Age'
       AND "campaign_item_criteria"."age_min" <= 17
       AND ("campaign_item_criteria"."age_max" IS NULL OR "campaign_item_criteria"."age_max" >= 17)
       THEN 1
  ELSE 0
END = 1

即使其他条件与用户的信息不匹配，只要一个标准与用户的信息匹配，它就会返回Campaign::Item，这也不起作用。< / p>

现在我们的想法已经不多了。我们是否有机会在纯SQL中按预期工作？有人有任何导致吗？

提前致谢！

Answer 1

为什么不在where子句中使用exists？（简写因为f ***再次输入所有内容）

SELECT ci.*
FROM campaign_items ci
WHERE exists (select 1
              from campaign_item_criteria cic
              where cic.campaign_item_id = ci.id
              and cic.type = '::gender'
              and (cic.gender = 'female' or cic.gender is null)
             )
and exists (select 1
              from campaign_item_criteria cic
              where cic.campaign_item_id = ci.id
              and cic.type = '::age'
              and (cic.age = '35' or cic.age is null)
             )

Answer 2

我能够找到一个完全符合我要求的查询：

SELECT DISTINCT "campaign_items".*
FROM "campaign_items"
INNER JOIN "campaign_item_criteria"
  ON "campaign_item_criteria"."campaign_item_id" = "campaign_items"."id"
WHERE
  (NOT EXISTS (SELECT 1
               FROM "campaign_item_criteria"
               WHERE "campaign_item_criteria"."campaign_item_id" = "campaign_items"."id"
                     AND "campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Gender')
   OR EXISTS (SELECT 1
              FROM "campaign_item_criteria"
              WHERE "campaign_item_criteria"."campaign_item_id" = "campaign_items"."id"
                    AND "campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Gender'
                    AND "campaign_item_criteria"."gender" = 'female'))
  AND (NOT EXISTS (SELECT 1
                   FROM "campaign_item_criteria"
                   WHERE "campaign_item_criteria"."campaign_item_id" = "campaign_items"."id"
                         AND "campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Age')
       OR EXISTS (SELECT 1
                  FROM "campaign_item_criteria"
                  WHERE "campaign_item_criteria"."campaign_item_id" = "campaign_items"."id"
                        AND "campaign_item_criteria"."type" = 'Campaign::Item::Criterium::Age'
                        AND "campaign_item_criteria"."age_min" <= 17
                        AND ("campaign_item_criteria"."age_max" IS NULL
                             OR "campaign_item_criteria"."age_max" >= 17)))

这样就可以查询2个条件并且它有4个子查询。我们已经知道我们最终会得到~10个不同的标准。因此，最终请求的总共20个子查询目前（有2个标准），数据库中需要大约2.5ms，2 Campaign::Item，数据库需要大约16ms和2 000 Campaign::Item。它并不像我们想象的那样具有指数性，因此我们会说它足够好＆＃39;。

我们现在要保留这个有没有人可以添加任何内容或改进任何路径？

仅当所有关联记录符合条件

2 个答案: