在 Rails 查询中包含 LIKE 子句的最佳方法是什么？

Question

What's the best way to include a LIKE clause in a Rails query ie something along the lines of (the completely incorrect):

 Question.where(:content => 'LIKE %farming%')

Answer 1

You'd use the syntax:

Question.where("content LIKE ?" , "%#{farming}%")

Answer 2

If this is Rails 3 you can use Arel's matches . This has the advantage of being database agnostic. For example:

Question.where(Question.arel_table[:content].matches("%#{string}%"))

This is somewhat clunky, but easily extracted to scopes, eg:

class Question

  def self.match_scope_condition(col, query)
    arel_table[col].matches("%#{query}%")
  end

  scope :matching, lambda {|*args|
    col, opts = args.shift, args.extract_options!
    op = opts[:operator] || :or
    where args.flatten.map {|query| match_scope_condition(col, query) }.inject(&op)
  }

  scope :matching_content, lambda {|*query|
    matching(:content, *query)
  }
end

Question.matching_content('farming', 'dancing') # farming or dancing
Question.matching_content('farming', 'dancing', :operator => :and) # farming and dancing
Question.matching(:other_column, 'farming', 'dancing') # same thing for a different col

Of course to join with "AND" you could just chain the scopes.

Edit: +1 to metawhere and squeel though (haven't tried latter but it looks cool) They both add this type of functionality and much more.

Answer 3

If you want really sexy conditions and and don't have problems with external dependencies, I highly recommend MetaWhere and it's successor Squeel :

# MetaWhere
Question.where(:content.like => '%farming%')

# MetaWhere with operators overloaded
Question.where(:content =~ '%farming%')

# Squeel
Question.where { :content.matches => '%farming%' }

# Squeel with operators overloaded
Question.where { :content =~ '%farming%' }