How to specify multiple values in where with AR query interface in rails3

Per section 2.2 of rails guide on Active Record query interface here:

which seems to indicate that I can pass a string specifying the condition(s), then an array of values that should be substituted at some point while the arel is being built. So I've got a statement that generates my conditions string, which can be a varying number of attributes chained together with either AND or OR between them, and I pass in an array as the second arg to the where method, and I get:

ActiveRecord::PreparedStateme开发者_StackOverflow社区ntInvalid: wrong number of bind variables (1 for 5)

which leads me to believe I'm doing this incorrectly. However, I'm not finding anything on how to do it correctly. To restate the problem another way, I need to pass in a string to the where method such as "table.attribute = ? AND table.attribute1 = ? OR table.attribute1 = ?" with an unknown number of these conditions anded or ored together, and then pass something, what I thought would be an array as the second argument that would be used to substitute the values in the first argument conditions string. Is this the correct approach, or, I'm just missing some other huge concept somewhere and I'm coming at this all wrong? I'd think that somehow, this has to be possible, short of just generating a raw sql string.

This is actually pretty simple:

Model.where(attribute: [value1,value2])

Sounds like you're doing something like this:

Model.where("attribute = ? OR attribute2 = ?", [value, value])

Whereas you need to do this:

# notice the lack of an array as the last argument
Model.where("attribute = ? OR attribute2 = ?", value, value)

Have a look at http://guides.rubyonrails.org/active_record_querying.html#array-conditions for more details on how this works.

Instead of passing the same parameter multiple times to where() like this

User.where(
  "first_name like ? or last_name like ? or city like ?", 
  "%#{search}%", "%#{search}%", "%#{search}%"
)

you can easily provide a hash

User.where(
  "first_name like :search or last_name like :search or city like :search",
  {search: "%#{search}%"}
)

that makes your query much more readable for long argument lists.

Sounds like you're doing something like this:

Model.where("attribute = ? OR attribute2 = ?", [value, value])

Whereas you need to do this:

#notice the lack of an array as the last argument
Model.where("attribute = ? OR attribute2 = ?", value, value) Have a

look at http://guides.rubyonrails.org/active_record_querying.html#array-conditions for more details on how this works.

Was really close. You can turn an array into a list of arguments with *my_list.

Model.where("id = ? OR id = ?", *["1", "2"])

OR

params = ["1", "2"]
Model.where("id = ? OR id = ?", *params)

Should work

If you want to chain together an open-ended list of conditions (attribute names and values), I would suggest using an arel table.

It's a bit hard to give specifics since your question is so vague, so I'll just explain how to do this for a simple case of a Post model and a few attributes, say title, summary, and user_id (i.e. a user has_many posts).

First, get the arel table for the model:

table = Post.arel_table

Then, start building your predicate (which you will eventually use to create an SQL query):

relation = table[:title].eq("Foo")
relation = relation.or(table[:summary].eq("A post about foo"))
relation = relation.and(table[:user_id].eq(5))

Here, table[:title], table[:summary] and table[:user_id] are representations of columns in the posts table. When you call table[:title].eq("Foo"), you are creating a predicate, roughly equivalent to a find condition (get all rows whose title column equals "Foo"). These predicates can be chained together with and and or.

When your aggregate predicate is ready, you can get the result with:

Post.where(relation)

which will generate the SQL:

SELECT "posts".* FROM "posts"
WHERE (("posts"."title" = "Foo" OR "posts"."summary" = "A post about foo")
AND "posts"."user_id" = 5)

This will get you all posts that have either the title "Foo" or the summary "A post about foo", and which belong to a user with id 5.

Notice the way arel predicates can be endlessly chained together to create more and more complex queries. This means that if you have (say) a hash of attribute/value pairs, and some way of knowing whether to use AND or OR on each of them, you can loop through them one by one and build up your condition:

relation = table[:title].eq("Foo")
hash.each do |attr, value|
  relation = relation.and(table[attr].eq(value))
  # or relation = relation.or(table[attr].eq(value)) for an OR predicate
end
Post.where(relation)

Aside from the ease of chaining conditions, another advantage of arel tables is that they are independent of database, so you don't have to worry whether your MySQL query will work in PostgreSQL, etc.

Here's a Railscast with more on arel: http://railscasts.com/episodes/215-advanced-queries-in-rails-3?view=asciicast

Hope that helps.

You can use a hash rather than a string. Build up a hash with however many conditions and corresponding values you are going to have and put it into the first argument of the where method.

WRONG This is what I used to do for some reason.

keys = params[:search].split(',').map!(&:downcase)
# keys are now ['brooklyn', 'queens']

query = 'lower(city) LIKE ?'

if keys.size > 1
  # I need something like this depending on number of keys 
  # 'lower(city) LIKE ? OR lower(city) LIKE ? OR lower(city) LIKE ?'
 query_array = []
 keys.size.times { query_array << query }
 #['lower(city) LIKE ?','lower(city) LIKE ?']
 query = query_array.join(' OR ')
 # which gives me 'lower(city) LIKE ? OR lower(city) LIKE ?'
end
# now I can query my model
# if keys size is one then keys are just 'brooklyn', 
# in this case it is  'brooklyn', 'queens'
# @posts = Post.where('lower(city) LIKE ? OR lower(city) LIKE ?','brooklyn', 'queens' )
@posts = Post.where(query, *keys )

now however - yes - it's very simple. as nfriend21 mentioned

Model.where(attribute: [value1,value2])

does the same thing