具有不同列的随机顺序

Question

I am creating a query which involves several joins, which causes some duplicates

@users = User.joins(...).where(...).select("users.id")

From that result I want to make the records distinct and in RANDOM() order

I can't seem to recreate that with activerecord.

With SQL it would look something like

SELECT DISTINCT users.*
from ( long complex query)
ORDER BY RANDOM()

Answer 1

One of the easiest things to do, rather than building complex queries in any framework, is to build the complex query with standard SQL and then wrap it in a view:

CREATE VIEW complex_stuff AS
  SELECT DISTINCT users.*
  FROM ( long complex query)
  ORDER BY RANDOM();

The view becomes a simple entity or class from which you pull the required columns, possibly filtering by some column ( SELECT a, b, c FROM complex_stuff WHERE d = ? ).