def add_conditions(conditions, new_condition, andor="AND")
  if conditions.nil?
    conditions = ["(#{new_condition})"]
  elsif Array === conditions
    conditions[0] += " #{andor} (#{new_condition})"
  elsif String === conditions
    conditions += " #{andor} (#{new_condition})"
  else
    raise "bug"
  end
  conditions
end


def concat(*ary)
  if ActiveRecord::Base.connection.adapter_name=="MySQL"
    "concat(#{ary.join(",")})"
  else
    "#{ary.join("||")}"
  end
end


def boolean_condition(name)
  if ActiveRecord::Base.connection.adapter_name=="SQLite"
    "#{name}=='t'"
  else
    name
  end
end