salary_history 记录了每次调薪，每行是一名员工在某个生效日期之后的月薪。取出每名员工最新（effective_date 最大）的那一条记录。
(emp_id, effective_date) 是主键，同一员工不会有两条生效日期相同的记录。输入
salary_history(emp_id, effective_date, salary)输出
列为 emp_id, effective_date, salary，行顺序不限。
salary_history hr/salary_history
| # | emp_idint64 | effective_datedate | salaryint64 |
|---|---|---|---|
| 1 | 1 | 2015-10-01 | 78400 |
| 2 | 1 | 2018-11-07 | 88200 |
| 3 | 1 | 2022-03-07 | 98000 |
| 4 | 2 | 2017-09-09 | 57600 |
| 5 | 2 | 2021-02-08 | 64800 |
| 6 | 2 | 2021-12-30 | 72000 |
| 7 | 3 | 2020-06-05 | 56000 |
| 8 | 3 | 2023-07-02 | 63000 |
| 9 | 3 | 2024-03-29 | 70000 |
| 10 | 4 | 2023-04-20 | 41600 |
| 11 | 4 | 2024-12-09 | 46800 |
| 12 | 4 | 2025-11-19 | 52000 |
| 13 | 5 | 2016-07-16 | 41600 |
| 14 | 5 | 2020-08-21 | 46800 |
| 15 | 5 | 2022-09-30 | 52000 |
| 16 | 6 | 2016-10-23 | 36000 |
| 17 | 6 | 2019-07-25 | 40500 |
| 18 | 6 | 2026-03-02 | 45000 |
| 19 | 7 | 2025-03-17 | 38400 |
| 20 | 7 | 2025-09-14 | 43200 |
| # | emp_idInt64 | effective_dateDate | salaryInt64 |
|---|---|---|---|
| 1 | 2 | 2021-12-30 | 72000 |
| 2 | 5 | 2022-09-30 | 52000 |
| 3 | 9 | 2025-08-25 | 39000 |
| 4 | 10 | 2025-12-13 | 39000 |
| 5 | 11 | 2025-04-30 | 26000 |
| 6 | 14 | 2025-02-20 | 41000 |
| 7 | 15 | 2024-05-21 | 27000 |
| 8 | 16 | 2023-02-04 | 44000 |
| 9 | 17 | 2024-04-07 | 38000 |
| 10 | 18 | 2025-09-17 | 25000 |
| 11 | 22 | 2024-03-11 | 36000 |
| 12 | 26 | 2025-05-15 | 30000 |
| 13 | 28 | 2025-05-26 | 24000 |
| 14 | 29 | 2025-06-11 | 47000 |
| 15 | 30 | 2026-03-06 | 53000 |
| 16 | 31 | 2025-12-20 | 38000 |
| 17 | 32 | 2024-01-22 | 46500 |
| 18 | 34 | 2025-05-18 | 26000 |
| 19 | 35 | 2022-08-09 | 37000 |
| 20 | 37 | 2026-05-02 | 23000 |
| 21 | 39 | 2025-05-04 | 46000 |
| 22 | 1 | 2022-03-07 | 98000 |
| 23 | 3 | 2024-03-29 | 70000 |
| 24 | 4 | 2025-11-19 | 52000 |
| 25 | 6 | 2026-03-02 | 45000 |
| 26 | 7 | 2026-04-22 | 48000 |
| 27 | 8 | 2026-06-16 | 46000 |
| 28 | 12 | 2024-02-13 | 41000 |
| 29 | 13 | 2025-05-16 | 33000 |
| 30 | 19 | 2026-01-24 | 31000 |
| 31 | 20 | 2024-01-30 | 31000 |
| 32 | 21 | 2024-01-26 | 29500 |
| 33 | 23 | 2025-07-07 | 12000 |
| 34 | 24 | 2022-04-07 | 61000 |
| 35 | 25 | 2026-02-24 | 37000 |
| 36 | 27 | 2020-10-07 | 22000 |
| 37 | 33 | 2024-03-21 | 66000 |
| 38 | 36 | 2025-02-22 | 28000 |
| 39 | 38 | 2024-04-05 | 25000 |
| 40 | 40 | 2026-08-19 | 28000 |