Essential Books

.distinct or .uniq

suggest change

If you want to remove duplicates from a result, you can use .distinct(): 

Customers.select(:country).distinct

This queries the database as follows: 

SELECT DISTINCT "customers"."country" FROM "customers"

.uniq() has the same effect. With Rails 5.0 it got deprecated and it will be removed from Rails with version 5.1. The reason is, that the word unique doesn’t have the same meaning as distinct and it can be misleading. Furthermore distinct is closer to the SQL syntax.

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ActiveRecord Query Interface:
* ActiveRecord Query Interface
* .where
* .where with an array
* Scopes
* Get first and last record
* where.not
* Ordering
* Includes
* .delete all
* ActiveRecord case insensitive search
* .find by
* .group and .count
* .distinct or .uniq
* Joins
* Limit and Offset
* ActiveRecord Bang methods
Table Of Contents
0 Getting started with Ruby on Rails
1 Routing
2 ActiveRecord
3 Views
4 ActiveRecord migrations
5 Rails best practices
6 Naming conventions
7 ActionCable
8 ActiveModel
9 User Authentication in Rails
10 ActiveRecord Associations
11 ActiveRecord validations
12 ActiveRecord Query Interface
13 ActionMailer
14 Rails generate commands
15 Configuration
16 I18N - internalization
17 Using Google Maps with Rails
18 File Uploads
19 Caching
20 ActionController
21 Configuration
22 Safe constantize
23 Rails 5
24 Authorization with CanCan
25 Mongoid
26 Gems
27 Change default timezone
28 Asset pipeline
29 Upgrading Rails
30 ActiveRecord locking
31 Debugging
32 Configure Angular with Rails
33 Rails logger
34 Prawn PDF
35 Rails API
36 Deploying a Rails app on Heroku
37 ActiveSupport
38 Form Helpers
39 ActiveRecord transactions
40 RSpec and Ruby on Rails
41 Decorator pattern
42 Elasticsearch
43 React with Rails
44 Rails cookbook
45 Multi-purpose ActiveRecord columns
46 Class organization
47 Shallow Routing
48 Model states AASM
49 Rails 5 API Authentication
50 Testing Rails Applications
51 Active Jobs
52 Rails frameworks over the years
53 Nested form
54 Factory Girl
55 CSV
56 Tools for code optimization and cleanup
57 ActiveJob
58 Active Model serializers
59 Rails Engine - Modular Rails
60 Single Table inheritance
61 ActiveRecord transactions
62 Turbolinks
63 Friendly ID
64 Securely storing authentications keys
65 Authenticate API using Devise
66 Integrating React.js with Rails using Hyperloop
67 Change a default Rails application environment
68 Reserved words
69 Rails-Engines
70 Adding an Amazon RDS
71 Payment features in Rails
72 Rails on docker
73 Contributors