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Activerecord Join Query and select in Rails

ruby
active-record
join-query
select
Nikita BarsukovbyNikita Barsukov·Nov 27, 2024
TLDR
# Because who doesn't want a piece of every Post, with a side of author_name? @posts = Post.joins(:author).select('posts.*, authors.name as author_name')

With this, you'll retrieve posts with author names using ActiveRecord. The inner join magic .joins(:author) fetches associated authors while .select('posts.*, authors.name as author_name') zeroes in on all post attributes and the author's name, conveniently labeled as author_name for each post record.

Getting your hands dirty - JOINs and SELECTs

When pulling the strings of ActiveRecord's .joins and .select, remember that an orchestra sounds good only when everyone follows the conductor's baton. Align your model definitions with your join and select methods and prepare to be awestruck.

Model Association - your rails map

Just like a railroad map connecting different towns, associations connect your models. Cross-verify to avoid any engine derailments - you wouldn’t want any ActiveModel::MissingAttributeError jumping at you, would you?

Column Aliases - the secret code talk

Bad guys in movies use codenames, so why can't your tables? Aliases come in handy when there's a risk of name collisions across tables. Post join-query, use these aliases, like author_name, to discreetly retrieve your data.

Pluck - grab, don't fetch

Sometimes you need to pluck the diamond from the lot, not the entire lot. .pluck transforms ActiveRecord::Relation objects into efficient arrays with specific column values. Call it the smart, selective grab.

Debug and Custom Queries

You wouldn't want to go on a heist without a proper plan, would you? Use .to_sql to review and debug your SQL strategies. For complex operations beyond the powers of ActiveRecord, ring up an old friend of yours - ActiveRecord::Base.connection.exec_query.

Going pro with ActiveRecord

Clarity with table names in query

Clarity fuels productivity. Whenever using the select function, specify both the table name and column name. This practice steers clear of confusion and boosts SQL query performance.

Associations - are your Rails well-oiled?

Treat joins as your highway routes - they're reliant on well-defined model associations. Keep these definitions in check before you crank up the join engine.

Alias - the double agent

Ever looked at an alias and thought, "Who's this guy?" Avoid such confusion through careful aliasing, because this secret agent can backfire!

Don't miss the columns!

All necessary columns are your Holy Grail. Omitting a column in your select statement is like forgetting your phone at home - you'll feel the world falling apart.