[英]Translation SQL query to ActiveRecord (Rails)
I have encountered difficulties in translating SQL query to ActiveRecord performance. 在将SQL查询转换为ActiveRecord性能时遇到了困难。 I would be grateful for their assistance!
我将感谢他们的协助!
SELECT MAX(distances.max) from
(SELECT max(distance)
FROM
(SELECT * from tracks WHERE car_id=1) t , locations l
WHERE t.id=l.track_id
GROUP BY track_id) distances;
def max_track_length
sql= Location.select("MAX(distance) as distance")
.joins("INNER JOIN tracks ON tracks.id=locations.track_id")
.where("tracks.car_id = ?", self.id).group(:track_id).to_sql
res=Car.from("(#{sql}) l").maximum("l.distance")
res||=0;
end
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