本文介绍了如何使用子查询或 find_by_sql 链接或组合范围的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
I would like to perform a query like
SELECT * FROM ( SELECT * FROM products ORDER BY price ASC ) AS s GROUP BY item;
which return the cheapest of all products for each item. Using this subquery is good because it can run in O(N logN) time.
So I can find this with find_by_sql, but it would be nice to be able to chain it with other scopes for Product.
Anyone know how to either write this as a scope or chain scoped and find_by_sql?
解决方案
You should be able to do something like
Product.from("(SELECT * FROM products ORDER BY price ASC) AS products").group(:item)
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