问题
I'm using Rails 5.0.1 and Postgresql as my database. I have a table with column :content which contains words.
The problem: When I'm looking for a specific word, I want to see if the word contains letters (chars) of my choice. Let's say i want to DB to return words containg letters "a", "b" and "c" (all of them, but with no specific order)
What I'm doing: I found that i could use
Word.where("content like ?", "%a%").where("content like ?", "%b%").where("content like ?", "%c%")
OR
Word.where("content like ? content like ? content like ?", "%a%", "%b%", "%c%")
In both cases even if i switch order of given letters/substrings it works fine, ex. both would find word "back", "cab" etc..
The question: Is there any better/more DRY way to do it? What if want to find word with 8 different letters? Do i have to use "content like ?" 8 times? Is it possible to pass arguments as an array? (let's assume i don't know how many letters user will input)
回答1:
PostgreSQL has a handy expr op all (array) expression so you can say things like:
where content like all (array['%a%', '%b%', '%c'])
as a short form of:
where content like '%a%'
and content like '%b%'
and content like '%c%'
Also, ActiveRecord will conveniently replace a ? placeholder with a comma-delimited list if you hand it a Ruby array. That lets you say things like:
Word.where('content like all (array[?])', %w[a b c].map { |c| "%#{c}%" })
and:
Word.where('content like all (array[?])', some_other_array.map { |c| "%#{c}%" })
回答2:
I found a solution:
letters = ["%a%", "%b%", "%c%"]
Word.where((['content LIKE ?'] * letters.size).join(' AND '), *letters)
This is easy and much better than I was using.
回答3:
I think the SIMILAR TO operator might help. It allows you to pass in a regular expression that you could construct on the fly.
letters = ['a', 'b', 'c']
pattern = "%(#{letters.join('|')})%"
Word.where("content SIMILAR TO ?", pattern)
来源：https://stackoverflow.com/questions/42124181/multiple-like-and-and-operators-in-rails-postgresql