Fred Heath discusses the many different many-to-many associations and how to handle each with ActiveRecord.
Master Many-to-Many Associations with ActiveRecord
N + 1: When More Queries Is a Good Thing
Parth Modi explains how he discovered that fixing the N + 1 Query Problem isn't always about reducing the number of queries. Sometimes, more queries is better.
A First Look at Atlas – the ORM That Delivers
Claudio takes a look at Atlas - a new type of ORM that doesn't oversell. If you're dying for a breath of fresh ORM air, check it out!
Yii 2.0 ActiveRecord Explained
Arno Slatius explains Yii 2.0's ActiveRecord, listing the features, novelties, upgrades and usage examples.
Complex Rails Forms with Nested Attributes