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Task 195: 
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"}
SQL Essentials for Data Analysis: A 50-Day Hands-on Challenge Book by Benjamin Bennett Alexander
SQL Essentials for Data Analysis: A 50-Day Hands-on Challenge Book by Benjamin Bennett Alexander
If you’re wondering whether you should learn SQL, the answer is simple: absolutely. SQL (Structured Query Language) is the language of data, and data powers every modern business. Whether you’re a data analyst, data scientist, business analyst, software engineer, financial analyst, product manager, or marketing professional, SQL helps you retrieve, analyze, and understand the information that drives decisions.