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    • main/kotlin/g3501_3600/s3580_find_consistently_improving_employees
    • test/kotlin/g3501_3600/s3580_find_consistently_improving_employees

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‎src/main/kotlin/g3501_3600/s3580_find_consistently_improving_employees/readme.md

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3580\. Find Consistently Improving Employees
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Medium
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Table: `employees`
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+-------------+---------+
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| Column Name | Type |
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+-------------+---------+
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| employee_id | int |
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| name | varchar |
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+-------------+---------+
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employee_id is the unique identifier for this table.
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Each row contains information about an employee.
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Table: `performance_reviews`
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+-------------+------+
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| Column Name | Type |
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+-------------+------+
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| review_id | int |
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| employee_id | int |
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| review_date | date |
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| rating | int |
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+-------------+------+
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review_id is the unique identifier for this table.
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Each row represents a performance review for an employee.
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The rating is on a scale of 1-5 where 5 is excellent and 1 is poor.
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Write a solution to find employees who have consistently improved their performance over **their last three reviews**.
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* An employee must have **at least** `3` **review** to be considered
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* The employee's **last** `3` **reviews** must show **strictly increasing ratings** (each review better than the previous)
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* Use the most recent `3` reviews based on `review_date` for each employee
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* Calculate the **improvement score** as the difference between the latest rating and the earliest rating among the last `3` reviews
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Return _the result table ordered by **improvement score** in **descending** order, then by **name** in **ascending** order_.
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The result format is in the following example.
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**Example:**
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**Input:**
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employees table:
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+-------------+----------------+
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| employee_id | name |
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+-------------+----------------+
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| 1 | Alice Johnson |
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| 2 | Bob Smith |
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| 3 | Carol Davis |
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| 4 | David Wilson |
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| 5 | Emma Brown |
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+-------------+----------------+
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performance\_reviews table:
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+-----------+-------------+-------------+--------+
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| review_id | employee_id | review_date | rating |
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+-----------+-------------+-------------+--------+
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| 1 | 1 | 2023-01-15 | 2 |
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| 2 | 1 | 2023-04-15 | 3 |
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| 3 | 1 | 2023-07-15 | 4 |
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| 4 | 1 | 2023-10-15 | 5 |
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| 5 | 2 | 2023-02-01 | 3 |
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| 6 | 2 | 2023-05-01 | 2 |
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| 7 | 2 | 2023-08-01 | 4 |
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| 8 | 2 | 2023-11-01 | 5 |
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| 9 | 3 | 2023-03-10 | 1 |
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| 10 | 3 | 2023-06-10 | 2 |
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| 11 | 3 | 2023-09-10 | 3 |
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| 12 | 3 | 2023-12-10 | 4 |
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| 13 | 4 | 2023-01-20 | 4 |
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| 14 | 4 | 2023-04-20 | 4 |
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| 15 | 4 | 2023-07-20 | 4 |
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| 16 | 5 | 2023-02-15 | 3 |
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| 17 | 5 | 2023-05-15 | 2 |
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+-----------+-------------+-------------+--------+
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**Output:**
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+-------------+----------------+-------------------+
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| employee_id | name | improvement_score |
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+-------------+----------------+-------------------+
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| 2 | Bob Smith | 3 |
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| 1 | Alice Johnson | 2 |
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| 3 | Carol Davis | 2 |
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+-------------+----------------+-------------------+
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**Explanation:**
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* **Alice Johnson (employee\_id = 1):**
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* Has 4 reviews with ratings: 2, 3, 4, 5
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* Last 3 reviews (by date): 2023-04-15 (3), 2023-07-15 (4), 2023-10-15 (5)
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* Ratings are strictly increasing: 3 → 4 → 5
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* Improvement score: 5 - 3 = 2
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* **Carol Davis (employee\_id = 3):**
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* Has 4 reviews with ratings: 1, 2, 3, 4
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* Last 3 reviews (by date): 2023-06-10 (2), 2023-09-10 (3), 2023-12-10 (4)
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* Ratings are strictly increasing: 2 → 3 → 4
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* Improvement score: 4 - 2 = 2
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* **Bob Smith (employee\_id = 2):**
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* Has 4 reviews with ratings: 3, 2, 4, 5
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* Last 3 reviews (by date): 2023-05-01 (2), 2023-08-01 (4), 2023-11-01 (5)
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* Ratings are strictly increasing: 2 → 4 → 5
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* Improvement score: 5 - 2 = 3
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* **Employees not included:**
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* David Wilson (employee\_id = 4): Last 3 reviews are all 4 (no improvement)
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* Emma Brown (employee\_id = 5): Only has 2 reviews (needs at least 3)
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The output table is ordered by improvement\_score in descending order, then by name in ascending order.

‎src/main/kotlin/g3501_3600/s3580_find_consistently_improving_employees/script.sql

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# Write your MySQL query statement below
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# #Medium #Database #2025_06_11_Time_449_ms_(91.67%)_Space_0.0_MB_(100.00%)
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WITH Ranked AS (
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SELECT
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e.employee_id,
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e.name,
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pr.review_date,
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pr.rating,
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RANK() OVER (
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PARTITION BY e.employee_id
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ORDER BY pr.review_date DESC
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) AS rnk,
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LAG(pr.rating) OVER (
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PARTITION BY e.employee_id
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ORDER BY pr.review_date DESC
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) AS lag_rating
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FROM employees e
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LEFT JOIN performance_reviews pr
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ON e.employee_id = pr.employee_id
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)
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SELECT
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employee_id,
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name,
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MAX(rating) - MIN(rating) AS improvement_score
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FROM Ranked
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WHERE rnk <= 3
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GROUP BY
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employee_id,
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name
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HAVING
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COUNT(*) = 3
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AND SUM(CASE WHEN lag_rating > rating THEN 1 ELSE 0 END) = 2
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ORDER BY
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improvement_score DESC,
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name ASC;

‎src/test/kotlin/g3501_3600/s3580_find_consistently_improving_employees/MysqlTest.kt

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package g3501_3600.s3580_find_consistently_improving_employees
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import org.hamcrest.CoreMatchers.equalTo
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import org.hamcrest.MatcherAssert.assertThat
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import org.junit.jupiter.api.Test
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import org.zapodot.junit.db.annotations.EmbeddedDatabase
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import org.zapodot.junit.db.annotations.EmbeddedDatabaseTest
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import org.zapodot.junit.db.common.CompatibilityMode
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import java.io.BufferedReader
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import java.io.FileNotFoundException
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import java.io.FileReader
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import java.sql.SQLException
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import java.util.stream.Collectors
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import javax.sql.DataSource
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@EmbeddedDatabaseTest(
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compatibilityMode = CompatibilityMode.MySQL,
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initialSqls = [
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(
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"CREATE TABLE employees(employee_id INTEGER, name VARCHAR(255)); " +
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"INSERT INTO employees (employee_id, name) VALUES" +
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" (1, 'Alice Johnson')," +
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" (2, 'Bob Smith')," +
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" (3, 'Carol Davis')," +
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" (4, 'David Wilson')," +
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" (5, 'Emma Brown');" +
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"CREATE TABLE performance_reviews(review_id INTEGER, employee_id INTEGER" +
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", review_date DATE, rating INTEGER); " +
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"INSERT INTO performance_reviews (review_id, employee_id, review_date, rating) VALUES" +
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" (1, 1, '2023-01-15', 2)," +
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" (2, 1, '2023-04-15', 3)," +
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" (3, 1, '2023-07-15', 4)," +
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" (4, 1, '2023-10-15', 5)," +
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" (5, 2, '2023-02-01', 3)," +
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" (6, 2, '2023-05-01', 2)," +
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" (7, 2, '2023-08-01', 4)," +
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" (8, 2, '2023-11-01', 5)," +
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" (9, 3, '2023-03-10', 1)," +
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" (10, 3, '2023-06-10', 2)," +
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" (11, 3, '2023-09-10', 3)," +
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" (12, 3, '2023-12-10', 4)," +
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" (13, 4, '2023-01-20', 4)," +
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" (14, 4, '2023-04-20', 4)," +
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" (15, 4, '2023-07-20', 4)," +
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" (16, 5, '2023-02-15', 3)," +
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" (17, 5, '2023-05-15', 2);"
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),
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],
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)
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internal class MysqlTest {
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@Test
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@Throws(SQLException::class, FileNotFoundException::class)
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fun testScript(@EmbeddedDatabase dataSource: DataSource) {
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dataSource.connection.use { connection ->
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connection.createStatement().use { statement ->
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statement.executeQuery(
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BufferedReader(
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FileReader(
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(
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"src/main/kotlin/g3501_3600/" +
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"s3580_find_consistently_improving_employees/" +
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"script.sql"
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),
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),
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)
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.lines()
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.collect(Collectors.joining("\n"))
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.replace("#.*?\\r?\\n".toRegex(), ""),
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).use { resultSet ->
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assertThat<Boolean>(resultSet.next(), equalTo<Boolean>(true))
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assertThat<String>(resultSet.getNString(1), equalTo<String>("2"))
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assertThat<String>(
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resultSet.getNString(2),
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equalTo<String>("Bob Smith"),
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)
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assertThat<String>(resultSet.getNString(3), equalTo<String>("3"))
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assertThat<Boolean>(resultSet.next(), equalTo<Boolean>(true))
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assertThat<String>(resultSet.getNString(1), equalTo<String>("1"))
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assertThat<String>(
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resultSet.getNString(2),
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equalTo<String>("Alice Johnson"),
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)
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assertThat<String>(resultSet.getNString(3), equalTo<String>("2"))
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assertThat<Boolean>(resultSet.next(), equalTo<Boolean>(true))
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assertThat<String>(resultSet.getNString(1), equalTo<String>("3"))
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assertThat<String>(
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resultSet.getNString(2),
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equalTo<String>("Carol Davis"),
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)
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assertThat<String>(resultSet.getNString(3), equalTo<String>("2"))
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assertThat<Boolean>(resultSet.next(), equalTo<Boolean>(false))
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}
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}
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}
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}
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}

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