Question

我们的rails应用中有3个表payment_logs，sourcings和purchasings。 payment_log属于采购或采购，但不属于同时。采购和采购都有一个col project_id。我们想要选择all payment_logs with its project_id = project_id_search（从搜索页面传递的project_id_search）。我们还需要一个ActiveRecord作为返回的结果集。以下是单个查询，假设payment_logs包含ActiveRecord结果集：

选择所有payment_logs及其采购的project_id = project_id_search

payment_logs = payment_logs.joins（：sourcing）.where（“sourcings.project_id =？”，project_id_search）
选择所有payment_logs及其购买的project_id = project_id_search

payment_logs = payment_logs。（：purchase）.where（“purchasings.project_id =？”，project_id_search）

我们需要联合1和2以获取其project_id = project_id_search的所有payment_log。什么是完成它的正确方法？我们没有在rails中找到union，find_by_sql返回的数组不是我们想要的。感谢。

Answer 1

payment_logs.where(["
  payment_logs.sourcing_id IN (
                                SELECT id FROM sourcings WHERE sourcings.project_id = ? 
                              ) 
  OR payment_logs.purchasing_id IN 
                              (
                                SELECT id FROM purchasings WHERE purchasings.project_id = ? 
                              )", project_id_search, project_id_search])

很多SQL，但它应该可以工作

选项2（两个SQL请求......）：

payment_logs = []
payment_logs << PaymentLog.joins(:sourcing).where("sourcings.project_id" => project_id_search)
payment_logs << PaymentLog.joins(:purchasing).where("purchasings.project_id" => project_id_search)
payment_logs.uniq! #In case some records have both a sourcing and a purchasing

选项3，使用squeel gem：https://github.com/ernie/squeel

PaymentLog.where{(source_id.in Sourcing.where(:project_id => project_id_search)) | (purchasing_id.in Purchasing.where(:project_id => project_id_search))}

我喜欢这个解决方案:) 此外，只要您对生成的SQL有疑问，从控制台或其他任何地方，您可以在ActiveRecord查询结束时添加.to_sql以双重检查生成的SQL

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