Rank Penguins by Body Mass

You're analyzing data from a study on penguins and need to divide them into three equally sized groups based on their body mass.

Write an SQL query that selects the species, island, and body_mass_g for each penguin from the little_penguins table. Additionally, add a new column named body_mass_class that assigns each penguin to one of three groups (terciles) based on their body_mass_g, with the lightest penguins in group 1 and the heaviest in group 3.