Question

While executing the below mysql query in rails

cnt = Domainurl.find_by_sql ["SELECT Max(`count`)FROM `domainurls` WHERE `domaindetail_id`= ?",@domain.id]
urlcr=Domainurl.find_by_sql ["SELECT * FROM `domainurls` WHERE `domaindetail_id` = ? AND `count` = ?",cnt.count]
urlcr.each do |cr|
  puts cr.url
end

I am getting error :

"error is: undefined method `closed?' for nil:NilClass"

Answer 1

the problem is at your last query

urlcr=Domainurl.find_by_sql ["SELECT * FROM `domainurls` WHERE `domaindetail_id` = ? AND `count` = ?",cnt.count]

you try to find something by 2 parameters ( domaindetail_id and count) but you provide only count. (you must provide domaindetail_id too)

urlcr=Domainurl.find_by_sql ["SELECT * FROM `domainurls` WHERE `domaindetail_id` = ? AND `count` = ?",@domain.id, cnt.count] #observe that I added @domain.id

You can rewrite that like

cnt = Domainurl.where(:domaindetail_id => @domain.id).maximum(:count) # this returns a number
urlcr=Domainurl.where("domaindetail_id = ? AND count = ?", @domain.id, cnt)