Added task 3580

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

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

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

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

src/test/java/g3501_3600/s3580_find_consistently_improving_employees/MysqlTest.java

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