Activerecord Arel OR condition

ruby

arel-techniques

active-record

sql-conditions

byAnton Shumikhin·Aug 22, 2024

Get straight into crafting OR conditions in ActiveRecord utilizing the power of Arel. Let's say you need to find Users with a first_name of 'Alice' OR a last_name of 'Bob'. Here's the direct route:

users = User.arel_table
query = User.where(users[:first_name].eq('Alice').or(users[:last_name].eq('Bob')))

Here Arel builds complex queries, while eq acts as the = from SQL, simplifying OR queries in ActiveRecord.

Arel techniques for condition chaining

Arel provides a flexible way to design intricate SQL conditions, exceeding the limitations of basic ActiveRecord queries. Suppose you have a need for more complex OR conditions. Here's how to achieve it:

table = User.arel_table
# Dude, where's my OR condition?
# Right here, chaining as complex as you need.
combined_conditions = table[:first_name].eq('Alice')
                                .or(table[:last_name].eq('Bob'))
                                .or(table[:status].eq('active'))

users = User.where(combined_conditions)

Always safeguard your code. Double-check the generated SQL with to_sql. "Trust but verify", as they say:

puts users.to_sql
# Presenting the grand SQL statement mightier than the Excalibur!

Intermixing Arel OR conditions with ActiveRecord where clauses might appear tricky. Beginning with Rails 5, ActiveRecord now accommodates the or method, making your code more elegant and legible:

# Just when you thought Rails could not get any cooler,
# ActiveRecord: "Hold my beer!"
admins_or_authors = User.where(kind: 'admin').or(User.where(kind: 'author'))

For earlier Rails versions or when logic gets murky, Arel comes to your aid. Merge Arel with ActiveRecord in harmony as shown below:

admins = User.where(kind: 'admin')
authors = User.where(kind: 'author')
combined = admins.where(admins.where_values.reduce(:or))
                .or(authors.where(authors.where_values.reduce(:or)))

Exploring advanced condition construction with Arel

Complex condition construction

For SQL queries as intricate as a Jackson Pollock painting, Arel becomes your paintbrush.

Method chaining

Harness the full potential of Arel's fluent interface and approach each method like a link in an unbroken chain.

Reduce: your secret uncrowned hero

When or doesn't hold the fort, turn to reduce(:or), coming to the rescue by compressing an array of conditions into a single encompassing condition.