53. Same City Pair

Medium Self Join

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

SELECT p1.first_name AS patient1, p2.first_name AS patient2, p1.city FROM patients p1 JOIN patients p2 ON p1.city = p2.city WHERE p1.patient_id < p2.patient_id;

SQL Editor

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Console Output

Console Terminal

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