356. Find Islands (Consecutive Dates)

Hard Infosys Advanced & Tricky

Query Rules

The query columns and order must match the expected result schema.
NULL values should be handled appropriately where applicable.
The grader compares output values and sorting order to evaluate.

Schema Browser

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patients

10 cols

patient_id

INTEGER

first_name

VARCHAR(30)

last_name

VARCHAR(30)

gender

CHAR(1)

birth_date

DATE

city

VARCHAR(30)

province_id

CHAR(2)

allergies

VARCHAR(80)

height

DECIMAL(3,0)

weight

DECIMAL(4,0)

doctors

4 cols

admissions

7 cols

province_names

2 cols

Reference Solution

Expected SQL

WITH distinct_dates AS (SELECT DISTINCT admission_date FROM admissions), grp AS (SELECT admission_date, DATE(admission_date, '-' || ROW_NUMBER() OVER (ORDER BY admission_date) || ' days') AS grp_key FROM distinct_dates) SELECT MIN(admission_date) AS island_start, MAX(admission_date) AS island_end, COUNT(*) AS days_in_island FROM grp GROUP BY grp_key ORDER BY island_start;

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Console Output

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