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Add new practice exercise: isbn-verifier (#109)
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‎config.json

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"prerequisites": [],
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"difficulty": 8
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},
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{
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"slug": "isbn-verifier",
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"name": "ISBN Verifier",
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"uuid": "a0a1cb68-b587-4d30-bf1c-819814847637",
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"practices": [],
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"prerequisites": [],
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"difficulty": 8
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},
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{
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"slug": "isogram",
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"name": "Isogram",

‎exercises/practice/isbn-verifier/.docs/instructions.md

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# Instructions
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The [ISBN-10 verification process][isbn-verification] is used to validate book identification numbers.
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These normally contain dashes and look like: `3-598-21508-8`
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## ISBN
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The ISBN-10 format is 9 digits (0 to 9) plus one check character (either a digit or an X only).
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In the case the check character is an X, this represents the value '10'.
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These may be communicated with or without hyphens, and can be checked for their validity by the following formula:
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```text
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(d₁ * 10 + d₂ * 9 + d₃ * 8 + d₄ * 7 + d₅ * 6 + d₆ * 5 + d₇ * 4 + d₈ * 3 + d₉ * 2 + d₁₀ * 1) mod 11 == 0
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```
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If the result is 0, then it is a valid ISBN-10, otherwise it is invalid.
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## Example
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Let's take the ISBN-10 `3-598-21508-8`.
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We plug it in to the formula, and get:
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```text
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(3 * 10 + 5 * 9 + 9 * 8 + 8 * 7 + 2 * 6 + 1 * 5 + 5 * 4 + 0 * 3 + 8 * 2 + 8 * 1) mod 11 == 0
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```
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Since the result is 0, this proves that our ISBN is valid.
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## Task
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Given a string the program should check if the provided string is a valid ISBN-10.
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Putting this into place requires some thinking about preprocessing/parsing of the string prior to calculating the check digit for the ISBN.
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The program should be able to verify ISBN-10 both with and without separating dashes.
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## Caveats
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Converting from strings to numbers can be tricky in certain languages.
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Now, it's even trickier since the check digit of an ISBN-10 may be 'X' (representing '10').
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For instance `3-598-21507-X` is a valid ISBN-10.
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[isbn-verification]: https://en.wikipedia.org/wiki/International_Standard_Book_Number

‎exercises/practice/isbn-verifier/.meta/config.json

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{
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"authors": [
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"jimmytty"
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],
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"files": {
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"solution": [
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"isbn-verifier.sql"
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],
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"test": [
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"isbn-verifier_test.sql"
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],
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"example": [
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".meta/example.sql"
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]
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},
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"blurb": "Check if a given string is a valid ISBN-10 number.",
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"source": "Converting a string into a number and some basic processing utilizing a relatable real world example.",
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"source_url": "https://en.wikipedia.org/wiki/International_Standard_Book_Number#ISBN-10_check_digit_calculation"
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}

‎exercises/practice/isbn-verifier/.meta/example.sql

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UPDATE "isbn-verifier"
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SET result = FALSE
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WHERE GLOB(
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'[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9X]',
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REPLACE(isbn, '-', '')
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) = 0
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;
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UPDATE "isbn-verifier"
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SET result = (
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WITH RECURSIVE verifier(isbn, digit, pos) AS (
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VALUES((
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WITH RECURSIVE cleaner(string, char) AS (
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VALUES(isbn, '')
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UNION ALL
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SELECT SUBSTRING(string, 2), SUBSTRING(string, 1, 1)
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FROM cleaner
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WHERE string <> ''
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)
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SELECT GROUP_CONCAT(char, '')
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FROM cleaner WHERE GLOB('[0-9X]', char)
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), '', 11)
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UNION ALL
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SELECT
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SUBSTRING(isbn, 2),
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IIF(SUBSTRING(isbn, 1, 1) = 'X', 10, SUBSTRING(isbn, 1, 1)),
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pos - 1
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FROM verifier
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WHERE isbn <> ''
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) SELECT SUM(digit * pos) % 11 = 0 FROM verifier WHERE digit <> ''
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)
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WHERE result ISNULL
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;

‎exercises/practice/isbn-verifier/.meta/tests.toml

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# This is an auto-generated file.
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#
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# Regenerating this file via `configlet sync` will:
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# - Recreate every `description` key/value pair
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# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
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# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
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# - Preserve any other key/value pair
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#
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# As user-added comments (using the # character) will be removed when this file
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# is regenerated, comments can be added via a `comment` key.
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[0caa3eac-d2e3-4c29-8df8-b188bc8c9292]
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description = "valid isbn"
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[19f76b53-7c24-45f8-87b8-4604d0ccd248]
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description = "invalid isbn check digit"
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[4164bfee-fb0a-4a1c-9f70-64c6a1903dcd]
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description = "valid isbn with a check digit of 10"
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[3ed50db1-8982-4423-a993-93174a20825c]
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description = "check digit is a character other than X"
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[9416f4a5-fe01-4b61-a07b-eb75892ef562]
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description = "invalid check digit in isbn is not treated as zero"
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[c19ba0c4-014f-4dc3-a63f-ff9aefc9b5ec]
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description = "invalid character in isbn is not treated as zero"
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[28025280-2c39-4092-9719-f3234b89c627]
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description = "X is only valid as a check digit"
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[f6294e61-7e79-46b3-977b-f48789a4945b]
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description = "valid isbn without separating dashes"
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[185ab99b-3a1b-45f3-aeec-b80d80b07f0b]
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description = "isbn without separating dashes and X as check digit"
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[7725a837-ec8e-4528-a92a-d981dd8cf3e2]
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description = "isbn without check digit and dashes"
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[47e4dfba-9c20-46ed-9958-4d3190630bdf]
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description = "too long isbn and no dashes"
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[737f4e91-cbba-4175-95bf-ae630b41fb60]
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description = "too short isbn"
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[5458a128-a9b6-4ff8-8afb-674e74567cef]
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description = "isbn without check digit"
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[70b6ad83-d0a2-4ca7-a4d5-a9ab731800f7]
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description = "check digit of X should not be used for 0"
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[94610459-55ab-4c35-9b93-ff6ea1a8e562]
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description = "empty isbn"
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[7bff28d4-d770-48cc-80d6-b20b3a0fb46c]
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description = "input is 9 characters"
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[ed6e8d1b-382c-4081-8326-8b772c581fec]
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description = "invalid characters are not ignored after checking length"
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[daad3e58-ce00-4395-8a8e-e3eded1cdc86]
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description = "invalid characters are not ignored before checking length"
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[fb5e48d8-7c03-4bfb-a088-b101df16fdc3]
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description = "input is too long but contains a valid isbn"

‎exercises/practice/isbn-verifier/create_fixture.sql

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DROP TABLE IF EXISTS "isbn-verifier";
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CREATE TABLE "isbn-verifier" (
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isbn TEXT NOT NULL,
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result BOOL
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);
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.mode csv
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.import ./data.csv "isbn-verifier"
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UPDATE "isbn-verifier" SET result = NULL;

‎exercises/practice/isbn-verifier/create_test_table.sql

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DROP TABLE IF EXISTS tests;
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CREATE TABLE IF NOT EXISTS tests (
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-- uuid and description are taken from the test.toml file
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uuid TEXT PRIMARY KEY,
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description TEXT NOT NULL,
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-- The following section is needed by the online test-runner
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status TEXT DEFAULT 'fail',
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message TEXT,
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output TEXT,
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test_code TEXT,
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task_id INTEGER DEFAULT NULL,
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-- Here are columns for the actual tests
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isbn TEXT NOT NULL,
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expected BOOL NOT NULL
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);
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INSERT INTO tests (uuid, description, isbn, expected)
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VALUES
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('0caa3eac-d2e3-4c29-8df8-b188bc8c9292','valid isbn','3-598-21508-8',TRUE),
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('19f76b53-7c24-45f8-87b8-4604d0ccd248','invalid isbn check digit','3-598-21508-9',FALSE),
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('4164bfee-fb0a-4a1c-9f70-64c6a1903dcd','valid isbn with a check digit of 10','3-598-21507-X',TRUE),
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('3ed50db1-8982-4423-a993-93174a20825c','check digit is a character other than X','3-598-21507-A',FALSE),
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('9416f4a5-fe01-4b61-a07b-eb75892ef562','invalid check digit in isbn is not treated as zero','4-598-21507-B',FALSE),
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('c19ba0c4-014f-4dc3-a63f-ff9aefc9b5ec','invalid character in isbn is not treated as zero','3-598-P1581-X',FALSE),
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('28025280-2c39-4092-9719-f3234b89c627','X is only valid as a check digit','3-598-2X507-9',FALSE),
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('f6294e61-7e79-46b3-977b-f48789a4945b','valid isbn without separating dashes','3598215088',TRUE),
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('185ab99b-3a1b-45f3-aeec-b80d80b07f0b','isbn without separating dashes and X as check digit','359821507X',TRUE),
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('7725a837-ec8e-4528-a92a-d981dd8cf3e2','isbn without check digit and dashes','359821507',FALSE),
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('47e4dfba-9c20-46ed-9958-4d3190630bdf','too long isbn and no dashes','3598215078X',FALSE),
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('737f4e91-cbba-4175-95bf-ae630b41fb60','too short isbn','00',FALSE),
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('5458a128-a9b6-4ff8-8afb-674e74567cef','isbn without check digit','3-598-21507',FALSE),
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('70b6ad83-d0a2-4ca7-a4d5-a9ab731800f7','check digit of X should not be used for 0','3-598-21515-X',FALSE),
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('94610459-55ab-4c35-9b93-ff6ea1a8e562','empty isbn','',FALSE),
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('7bff28d4-d770-48cc-80d6-b20b3a0fb46c','input is 9 characters','134456729',FALSE),
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('ed6e8d1b-382c-4081-8326-8b772c581fec','invalid characters are not ignored after checking length','3132P34035',FALSE),
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('daad3e58-ce00-4395-8a8e-e3eded1cdc86','invalid characters are not ignored before checking length','3598P215088',FALSE),
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('fb5e48d8-7c03-4bfb-a088-b101df16fdc3','input is too long but contains a valid isbn','98245726788',FALSE);

‎exercises/practice/isbn-verifier/data.csv

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"3-598-21508-8",""
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"3-598-21508-9",""
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"3-598-21507-X",""
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"3-598-21507-A",""
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"4-598-21507-B",""
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"3-598-P1581-X",""
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"3-598-2X507-9",""
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"3598215088",""
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"359821507X",""
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"359821507",""
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"3598215078X",""
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"00",""
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"3-598-21507",""
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"3-598-21515-X",""
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"",""
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"134456729",""
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"3132P34035",""
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"3598P215088",""
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"98245726788",""

‎exercises/practice/isbn-verifier/isbn-verifier.sql

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-- Schema: CREATE TABLE "isbn-verifier" (isbn TEXT NOT NULL, result BOOL);
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-- Task: update the isbn-verifier table and set the result based on the isbn.

‎exercises/practice/isbn-verifier/isbn-verifier_test.sql

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-- Create database:
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.read ./create_fixture.sql
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-- Read user student solution and save any output as markdown in user_output.md:
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.mode markdown
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.output user_output.md
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.read ./isbn-verifier.sql
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.output
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-- Create a clean testing environment:
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.read ./create_test_table.sql
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-- Comparison of user input and the tests updates the status for each test:
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UPDATE tests
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SET status = 'pass'
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FROM (SELECT isbn, result FROM "isbn-verifier") AS actual
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WHERE (actual.isbn, actual.result) = (tests.isbn, tests.expected);
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-- Update message for failed tests to give helpful information:
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UPDATE tests
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SET message = (
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'Result for "'
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|| tests.isbn
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|| '"'
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|| ' is <' || COALESCE(actual.result, 'NULL')
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|| '> but should be <' || tests.expected || '>'
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)
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FROM (SELECT isbn, result FROM "isbn-verifier") AS actual
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WHERE actual.isbn = tests.isbn AND tests.status = 'fail';
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-- Save results to ./output.json (needed by the online test-runner)
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.mode json
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.once './output.json'
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SELECT description, status, message, output, test_code, task_id
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FROM tests;
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-- Display test results in readable form for the student:
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.mode table
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SELECT description, status, message
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FROM tests;

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