README_EN.md

1112. Highest Grade For Each Student

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Description

Table: Enrollments

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| student_id    | int     |
| course_id     | int     |
| grade         | int     |
+---------------+---------+
(student_id, course_id) is the primary key of this table.

 

Write a SQL query to find the highest grade with its corresponding course for each student. In case of a tie, you should find the course with the smallest course_id.

Return the result table ordered by student_id in ascending order.

The query result format is in the following example.

 

Example 1:

Input: 
Enrollments table:
+------------+-------------------+
| student_id | course_id | grade |
+------------+-----------+-------+
| 2          | 2         | 95    |
| 2          | 3         | 95    |
| 1          | 1         | 90    |
| 1          | 2         | 99    |
| 3          | 1         | 80    |
| 3          | 2         | 75    |
| 3          | 3         | 82    |
+------------+-----------+-------+
Output: 
+------------+-------------------+
| student_id | course_id | grade |
+------------+-----------+-------+
| 1          | 2         | 99    |
| 2          | 2         | 95    |
| 3          | 3         | 82    |
+------------+-----------+-------+

Solutions

SQL

SELECT
  student_id,
  course_id,
  grade
FROM (SELECT
  *,
  RANK() OVER (PARTITION BY student_id ORDER BY grade DESC, course_id) rk
FROM Enrollments) a
WHERE a.rk = 1;