在Redshift/PostgreSQL中使用Last_Value窗口函数

LAST_VALUE (expression) OVER (
    [PARTITION BY partition_expression, ... ]
    [ORDER BY sort_expression [ASC | DESC], ... ]
    [ROWS { UNBOUNDED PRECEDING | value PRECEDING | CURRENT ROW | value FOLLOWING | UNBOUNDED FOLLOWING }]
)

+------+-------+
| year | sales |
+------+-------+
| 2019 |  100  |
| 2020 |  200  |
| 2021 |  NULL |
| 2022 |  300  |
+------+-------+

SELECT year, sales, LAST_VALUE(sales) OVER (ORDER BY year) AS last_sales
FROM sales;

+------+-------+------------+
| year | sales | last_sales |
+------+-------+------------+
| 2019 |  100  |    100     |
| 2020 |  200  |    200     |
| 2021 |  NULL |    300     |
| 2022 |  300  |    300     |
+------+-------+------------+