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2004. The Number of Seniors and Juniors to Join the Company

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Description

Table: Candidates

+-------------+------+
| Column Name | Type |
+-------------+------+
| employee_id | int  |
| experience  | enum |
| salary      | int  |
+-------------+------+
employee_id is the primary key column for this table.
experience is an enum with one of the values ('Senior', 'Junior').
Each row of this table indicates the id of a candidate, their monthly salary, and their experience.

 

A company wants to hire new employees. The budget of the company for the salaries is 70000. The company's criteria for hiring are:

1. Hiring the largest number of seniors.
2. After hiring the maximum number of seniors, use the remaining budget to hire the largest number of juniors.

Write an SQL query to find the number of seniors and juniors hired under the mentioned criteria.

Return the result table in any order.

The query result format is in the following example.

 

Example 1:

Input: 
Candidates table:
+-------------+------------+--------+
| employee_id | experience | salary |
+-------------+------------+--------+
| 1           | Junior     | 10000  |
| 9           | Junior     | 10000  |
| 2           | Senior     | 20000  |
| 11          | Senior     | 20000  |
| 13          | Senior     | 50000  |
| 4           | Junior     | 40000  |
+-------------+------------+--------+
Output: 
+------------+---------------------+
| experience | accepted_candidates |
+------------+---------------------+
| Senior     | 2                   |
| Junior     | 2                   |
+------------+---------------------+
Explanation: 
We can hire 2 seniors with IDs (2, 11). Since the budget is 70000 and the sum of their salaries is 40000, we still have 30000 but they are not enough to hire the senior candidate with ID 13.
We can hire 2 juniors with IDs (1, 9). Since the remaining budget is 30000 and the sum of their salaries is 20000, we still have 10000 but they are not enough to hire the junior candidate with ID 4.

Example 2:

Input: 
Candidates table:
+-------------+------------+--------+
| employee_id | experience | salary |
+-------------+------------+--------+
| 1           | Junior     | 10000  |
| 9           | Junior     | 10000  |
| 2           | Senior     | 80000  |
| 11          | Senior     | 80000  |
| 13          | Senior     | 80000  |
| 4           | Junior     | 40000  |
+-------------+------------+--------+
Output: 
+------------+---------------------+
| experience | accepted_candidates |
+------------+---------------------+
| Senior     | 0                   |
| Junior     | 3                   |
+------------+---------------------+
Explanation: 
We cannot hire any seniors with the current budget as we need at least 80000 to hire one senior.
We can hire all three juniors with the remaining budget.

Solutions

SQL

# Write your MySQL query statement below
WITH
    s AS (
        SELECT
            employee_id,
            SUM(salary) OVER (ORDER BY salary) AS cur
        FROM Candidates
        WHERE experience = 'Senior'
    ),
    j AS (
        SELECT
            employee_id,
            IFNULL(
                SELECT
                    MAX(cur)
                FROM s
                WHERE cur <= 70000,
                0
            ) + SUM(salary) OVER (ORDER BY salary) AS cur
        FROM Candidates
        WHERE experience = 'Junior'
    )
SELECT
    'Senior' AS experience,
    COUNT(employee_id) AS accepted_candidates
FROM s
WHERE cur <= 70000
UNION ALL
SELECT
    'Junior' AS experience,
    COUNT(employee_id) AS accepted_candidates
FROM j
WHERE cur <= 70000;