Ruby on Rails:有没有办法从数据库中提取项目并按指定顺序返回它们? [英] Ruby on Rails: Is there any way to pull items from the database and have them returned in a specified order?

问题描述

我有一组物品 ID，item_ids.

I have an array of item ID's, item_ids.

我将此数组传递给 ActiveRecord 查询以从数据库中检索相应的项目:Item.where(:id => item_ids)

I'm passing this array into an ActiveRecord query to retrieve the corresponding items from the database: Item.where(:id => item_ids)

有什么方法可以让返回的项目按照通过 item_ids 数组传入的顺序返回?

Is there any way to get the items returned in the same order as passed in via the item_ids array?

如果有什么不同，我使用 Ruby on Rails 3.0.12，将 PostgreSQL 作为我的数据库.

If it makes a difference, I'm on Ruby on Rails 3.0.12 with PostgreSQL as my database.

推荐答案

可以让数据库做排序，避免多个index 调用，您只需要记住 SQL ORDER BY 由 表达式 排序，而不是列:

You can get the database to do the sorting and avoid multiple index calls, you just have to remember that an SQL ORDER BY orders by an expression, not a column:

whens = item_ids.collect.with_index { |id, i| "when #{id} then #{i}" }.join(' ')
items = Item.where(:id => item_ids).order("case id #{whens} end")

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