find vs find_by vs where

find vs find_by vs where

I am new to rails. What I see that there are a lot of ways to find a record:

1. find_by_()
2. find(:first, :conditions => { => }
3. where( => ).first

And it looks like all of them end up generating exactly the same SQL. Also, I believe the same is true for finding multiple records:

1. find_all_by_()
2. find(:all, :conditions => { => }
3. where( => )

Is there a rule of thumb or recommendation on which one to use?

Answer by evanbikes for find vs find_by vs where

Both #2s in your lists are being deprecated. You can still use find(params[:id]) though.

Generally, where() works in most situations.

Here's a great post: http://m.onkey.org/active-record-query-interface

Answer by John for find vs find_by vs where

Use whichever one you feel suits your needs best.

The find method is usually used to retrieve a row by ID:

Model.find(1)  

Other uses of find are usually replaced with things like this:

Model.all  Model.first  

Find_by is used as a helper when you're searching for information within a column, and it maps to such with naming conventions. For instance, if you have a column named name in your database, you'd use the following syntax:

Model.find_by_name("Bob")  

However, I believe find_by is being deprecated.

.where is more of a catch all that lets you use a bit more complex logic for when the conventional helpers won't do.

Answer by Kasumi for find vs find_by vs where

There is a difference between find and find_by in that find will return an error if not found, whereas find_by will return null.

Sometimes it is easier to read if you have a method like find_by email: "haha", as opposed to .where(email: some_params).first.

Answer by MikeAndr for find vs find_by vs where

where returns ActiveRecord::Relation

Now take a look at find_by realization:

def find_by    where(*args).take  end  

As you can see find_by is the same as where but it returns only one record. This method should be used for getting 1 record and where should be used for getting all records with some conditions.

Answer by Agis for find vs find_by vs where

Since Rails 4 you can do:

User.find_by(name: 'Bob')  

which is the equivalent find_by_name in Rails 3.

Use #where when #find and #find_by are not enough.

Answer by Leonard Kakande for find vs find_by vs where

The accepted answer generally covers it all, but I'd like to add something, just incase you are planning to work with the model in a way like updating, and you are retrieving a single record(whose id you do not know), Then find_by is the way to go, because it retrieves the record and does not put it in an array

irb(main):037:0> @kit = Kit.find_by(number: "3456")    Kit Load (0.9ms)  SELECT "kits".* FROM "kits" WHERE "kits"."number" =    '3456' LIMIT 1  => #    irb(main):038:0> @kit.update(job_id: 2)  (0.2ms)  BEGIN Kit Exists (0.4ms)  SELECT 1 AS one FROM "kits" WHERE    ("kits"."number" = '3456' AND "kits"."id" != 1) LIMIT 1 SQL (0.5ms)     UPDATE "kits" SET "job_id" = $1, "updated_at" = $2 WHERE  "kits"."id" =   1  [["job_id", 2], ["updated_at", Tue, 12 May 2015 07:16:58 UTC +00:00]]   (0.6ms)  COMMIT => true  

but if you use where then you can not update it directly

irb(main):039:0> @kit = Kit.where(number: "3456")  Kit Load (1.2ms)  SELECT "kits".* FROM "kits" WHERE "kits"."number" =    '3456' => #]>    irb(main):040:0> @kit.update(job_id: 3)  ArgumentError: wrong number of arguments (1 for 2)  

in such a case you would have to specify it like this

irb(main):043:0> @kit[0].update(job_id: 3)  (0.2ms)  BEGIN Kit Exists (0.6ms)  SELECT 1 AS one FROM "kits" WHERE   ("kits"."number" = '3456' AND "kits"."id" != 1) LIMIT 1 SQL (0.6ms)     UPDATE "kits" SET "job_id" = $1, "updated_at" = $2 WHERE "kits"."id" = 1    [["job_id", 3], ["updated_at", Tue, 12 May 2015 07:28:04 UTC +00:00]]  (0.5ms)  COMMIT => true  

Answer by sweety mehta for find vs find_by vs where

Apart from accepted answer, following is also valid

Model.find() can accept array of ids, and will return all records which matches. Model.find_by_id(123) also accept array but will only process first id value present in array

Model.find([1,2,3])  Model.find_by_id([1,2,3])  

Answer by Nikhil Mohadikar for find vs find_by vs where

Suppose I have a model User

1. User.find(id)

Returns a row pointed by the id. So suppose, if id = 1, then it will return first row. Return type will be User object.

2. User.find_by(email:"abc@xyz.com")

Returns first row with matching attribute or email in this case. Return type will be User object again.

3. User.where(project_id:1)

Returns all users in users table where attribute matches. Here return type will be array of User objects.

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