如何使用Ruby on Rails找到列中最长的字符串？

Question

Ruby中从列中找到最长字符串的最有效方法是什么X？

更新:

这也是有效的:

def self.length_of_longest_number
  Invoice.order("LENGTH(number) DESC").first.number.length
end

只是想知道是否有效.如果它适用于MySQL 和 Postgres ......

Answer 1

这也是有效的:

def self.length_of_longest_number
  Invoice.order("LENGTH(number) DESC").first.number.length
end

只是想知道是否有效.如果它适用于MySQL 和 Postgres ......

Answer 2

# Change your model name and field to your needs
Participant.order("MAX(CHAR_LENGTH(first_name)) desc").limit(1)

# works too:
Participant.order("MAX(CHAR_LENGTH(first_name)) desc").first

# and this is the most efficient to get the field directly:
Participant.limit(1).order("MAX(CHAR_LENGTH(first_name)) desc").pluck(:first_name)