订购和限制 [英] order by and limit

问题描述

我需要做以下查询:

SELECT * FROM "specimens" ORDER BY distribution_sheet_id DESC LIMIT 10

我已经把:

<%=  Specimen.last(:order => :distribution_sheet_id).id  %>

我喜欢输出'limit 10'而不是limit 1.我想它是.last，但我可以用其他方式表达它来限制10.

I like to output 'limit 10' not limit 1. I suppose its the .last, but can I express it in other way to limit 10.

谢谢

推荐答案

假设您使用的是 Rails 3

Assuming you are using Rails 3

<%= Specimen.limit(10).order("distribution_sheet_id").all %>

请注意，如果限制超过1条记录，最后不能调用#id，因为结果是一个数组.

Please note that if you limit to more than 1 record, you can't call #id at the end because the result is an array.

获取所有ID

<%= Specimen.limit(10).order("distribution_sheet_id").map(&:id) %>

<小时>

对于 Rails 2.3，使用旧的基于哈希的条件.

---

For Rails 2.3 use the old hash-based conditions.

<%= Specimen.all(:order => "distribution_sheet_id", :limit => 10) %>

同样适用于 id

<%= Specimen.all(:order => "distribution_sheet_id", :limit => 10).map(&:id) %>

这里我使用 #to_sentence 方法来连接所有 ID.根据您的用例调整代码.

Here I'm using the #to_sentence method to join all ID. Adapt the code according to your use case.

<%= Specimen.all(:order => "distribution_sheet_id", :limit => 10).map(&:id).to_sentence %>

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