We are going to do the Transform step of an Extract-Transform-Load.


Extract-Transform-Load (ETL) is a fancy way of saying, "We have some crufty, legacy data over in this system, and now we need it in this shiny new system over here, so we're going to migrate this."

(Typically, this is followed by, "We're only going to need to run this once." That's then typically followed by much forehead slapping and moaning about how stupid we could possibly be.)

The goal

We're going to extract some Scrabble scores from a legacy system.

The old system stored a list of letters per score:

  • 1 point: "A", "E", "I", "O", "U", "L", "N", "R", "S", "T",
  • 2 points: "D", "G",
  • 3 points: "B", "C", "M", "P",
  • 4 points: "F", "H", "V", "W", "Y",
  • 5 points: "K",
  • 8 points: "J", "X",
  • 10 points: "Q", "Z",

The shiny new Scrabble system instead stores the score per letter, which makes it much faster and easier to calculate the score for a word. It also stores the letters in lower-case regardless of the case of the input letters:

  • "a" is worth 1 point.
  • "b" is worth 3 points.
  • "c" is worth 3 points.
  • "d" is worth 2 points.
  • Etc.

Your mission, should you choose to accept it, is to transform the legacy data format to the shiny new format.


A final note about scoring, Scrabble is played around the world in a variety of languages, each with its own unique scoring table. For example, an "E" is scored at 2 in the Māori-language version of the game while being scored at 4 in the Hawaiian-language version.

jq Tips

This exercise is about taking an input object and transforming it into a new object. A couple of builtin functions that may help:

  • to_entries
    • this function takes an object as input
    • it outputs an array -- each array element is an object {"key": "K", "value": V}
      • each K is a key from the input object
      • each V is K's corresponding value.
  • from_entries
    • the inverse operation
    • takes an array of {"key": K, "value": V} objects and constructs an object

An example:

jq -n '
        "username": "glennj",
        "tracks": ["bash", "awk", "jq"],
        "reputation": 123
    | to_entries


    "key": "username",
    "value": "glennj"
    "key": "tracks",
    "value": ["bash", "awk", "jq"]
    "key": "reputation",
    "value": 123
Last updated 25 January 2023
Edit via GitHub The link opens in a new window or tab
jq Exercism

Ready to start ETL?

Sign up to Exercism to learn and master jq with 12 concepts, 46 exercises, and real human mentoring, all for free.