Active Record Querying Methods Lab

Objectives

1. Create a table using ActiveRecord.
2. Use Active Record's querying methods.

Overview

In this lab, we'll be working in a TV show domain. We have a TV show model, the Show class, and a shows table that you'll create in your database.

You'll be required not only to write a migration that creates a shows table and gives the Show class certain attributes, but also to use Active Record's querying methods.

Active Record Querying Methods

Active Record makes it easy to ask our database for certain information and datasets by providing a bunch of built-in methods for us. For example, we can request the sum of all of the values of a particular column with the #sum method:

ClassName.sum(:column_name)

We can query our database based on certain conditions using the #where method.

Let's say we have a Song class and table and each song has a number_of_stars rating attribute. We could query for songs with more than 3 stars like this:

Song.where("number_of_stars > ?", 3)

Let's look at one more example: Let's say we want to query our database for the lowest value in the number_of_stars column, i.e., the lowest rating that any song has:

Song.minimum(:number_of_stars)

You'll be writing methods that rely on Active Record methods like #minimum, #sum, and #where to get these tests passing.

Use the following resources to help you find the Active Record query methods that will help you pass these tests:

• Calculations
• Ordering
• Conditions

Instructions

Migration

• Run mkdir db and then mkdir db/migrate to create the migrate folder within db. Then create a file in the db/migrate folder called 001_create_shows.rb. In this file, write the migration code to create a shows table. The table should have name, network, day, and rating columns. name, network, and day have a datatype of string, and rating has a datatype of integer.

• Create an app folder with a models folder within it, and then create a file, show.rb, in app/models. In this file, you will define a Show class that inherits from ActiveRecord::Base.

• Now we need to create a second migration to add another column to our shows table. In the db/migrate folder, create another file, 002_add_season_to_shows.rb, and write a migration to add a column, season, to the shows table. The datatype of this column is string.

Note: This lab is using ActiveRecord 5.2. You will need to specify this version in your migrations by having your classes inherit from ActiveRecord::Migration[5.2].

Methods

You'll be defining the following methods:

• highest_rating: this method should return the highest value in the ratings column. hint: if there is a minimum Active Record method, might there be a maximum method?

• most_popular_show: this method should return the show with the highest rating. hint: use the highest_rating method as a helper method.

• lowest_rating: returns the lowest value in the ratings column.

• least_popular_show: returns the show with the lowest rating.

• ratings_sum: returns the sum of all of the ratings.

• popular_shows: returns an array of all of the shows that have a rating greater than 5. hint: use the where Active Record method.

• shows_by_alphabetical_order: returns an array of all of the shows sorted in alphabetical order according to their names. hint: use the order Active Record method.