ActiveRecord 3“正在”哪里查询
执行 IS IN 查询的最佳方法是什么，尤其是在涉及联接时？
目前，我有类似以下内容：
Table1.joins(:table2).where( { :table2s => { :ident => params[:idents].split(',') } } )
这有效并完成了工作。由此产生的 WHERE 子句就像
WHERE "table2s"."ident" IS IN ('a','b','c')
我觉得这样会更干净：
Table1.joins(:table2).where("table2s.ident IS IN ?", params[:idents]:split(','))
有没有办法避免第一种样式并使用更像第二种样式的东西？ （即，where 方法识别数组并使用 IS IN 而不是“=”运算符）
What's the best way to do IS IN queries, especially when involving a join?
Currently, I have something like the following:
Table1.joins(:table2).where( { :table2s => { :ident => params[:idents].split(',') } } )
This works and gets the job done. The resulting WHERE clause is something like
WHERE "table2s"."ident" IS IN ('a','b','c')
I feel like this would be cleaner though:
Table1.joins(:table2).where("table2s.ident IS IN ?", params[:idents]:split(','))
Is there a way to avoid the first style and use something more like the second style? (i.e., the where method recognizes the array and uses IS IN rather than '=' operator)
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评论（2）
让查询编译器为您执行此操作通常是更好的方法，因为它可以处理您可能忘记的情况，例如传递
nil值并最终得到错误的IS IN( NULL)而不是IS NULL。不过，您可以清理您的语句：更进一步，您可以将其简化为：
您可以通过编写封装它的作用域来进一步清理它，而不是按原样使用它。
Letting the query compiler do it for you is generally a better way to do it as it will handle cases you might forget, such as passing a
nilvalue and ending up with an erroneousIS IN(NULL)instead ofIS NULL. You can clean up your statement, though:Taking this a step further, you can reduce it to:
You could further clean this up by writing a scope that encapsulates this instead of using this as-is.
你不需要分裂。 ActiveRecord 足够智能，可以理解数组，因此您只需要
Table1.joins(:table2).where( { :table2s => { :ident => params[:idents]}})。事实上，你不需要嵌套。
Table1.joins(:table2).where('table2s.ident' => params[:idents])应该可以找到。阿雷尔真是太聪明了！You don't need the split. ActiveRecord is smart enough to understand arrays, so all you need is
Table1.joins(:table2).where( { :table2s => { :ident => params[:idents]}}).In fact, you don't need the nesting.
Table1.joins(:table2).where('table2s.ident' => params[:idents])should work find. Arel is pretty smart!