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Task 196: 
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.

Use SQLite syntax to write your answer. Descriptions of tables are provided in the right pane.

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Querynomicon (SQLite)

A compact database for learning the basics of SQL.

The Querynomicon database tables:

department - table of departments.
  • identDepartment ID
  • nameDepartment name
  • buildingBuilding name
ident name building
gen Genetics Chesson
little_penguins - table of little penguins.
  • speciesPenguin species
  • islandIsland of residence
  • bill_length_mmBill length, mm
  • bill_depth_mmBill depth, mm
  • flipper_length_mmFlipper length, mm
  • body_mass_gBody mass, g
  • sexSex
species island bill_length_mm bill_depth_mm flipper_length_mm body_mass_g sex
Gentoo Biscoe 52.1 17 230 5550 MALE
penguins - table of penguins.
  • speciesPenguin species
  • islandIsland of residence
  • bill_length_mmBill length, mm
  • bill_depth_mmBill depth, mm
  • flipper_length_mmFlipper length, mm
  • body_mass_gBody mass, g
  • sexSex
species island bill_length_mm bill_depth_mm flipper_length_mm body_mass_g sex
Gentoo Biscoe 52.1 17 230 5550 MALE
staff - table of employees.
  • identEmployee number
  • personalEmployee first name
  • familyEmployee last name
  • deptDepartment
  • ageAge
ident personal family dept age
7 Abram Chokshi gen 23
machine - table of machines.
  • identMachine ID
  • nameMachine name
  • detailsJSON with details
ident name details
1 WY401 {"acquired": "2023-05-01"}
2 Inphormex {"acquired": "2021-07-15", "refurbished": "2023-10-22"}
3 AutoPlate 9000 {"note": "needs software update"}
Learning SQL: Generate, Manipulate, and Retrieve Data by Alan Beaulieu
Learning SQL: Generate, Manipulate, and Retrieve Data by Alan Beaulieu
As data floods into your company, you need to put it to work right away―and SQL is the best tool for the job. With the latest edition of this introductory guide, author Alan Beaulieu helps developers get up to speed with SQL fundamentals for writing database applications, performing administrative tasks, and generating reports. You’ll find new chapters on SQL and big data, analytic functions, and working with very large databases.