This guide covers different ways to retrieve data from the database using Active Record.After reading this guide, you will know: How to find records using a variety of methods and conditions. How to specify the order, retrieved attributes, grouping, and other properties of the found records. How to retrieve data efficiently. How to join tables and work with data from multiple tables. How to use scopes to create reusable query logic. How to check for the existence of particular records. How to perform calculations on Active Record models. How to use locking mechanisms for concurrent access control. How to run explain to analyze queries.