[英]Translation SQL query to ActiveRecord (Rails)
在將SQL查詢轉換為ActiveRecord性能時遇到了困難。 我將感謝他們的協助!
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
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.