添加具有先前日期的列（不等于当前日期）[SQL，PrestoDB]

Question

我有一个 table 这样的：

current_date	user_id
2021-10-01	1
2021-10-02	1
2021-10-02	1
2021-10-09	1
2021-10-15	1
2021-10-01	2
2021-10-01	2
2021-10-04	2
2021-10-04	2
2021-10-04	2
2021-10-11	2
2021-10-11	2

我想再添加一列之前的日期（不等于当前日期）。

所需的 table 应如下所示：

current_date	user_id	previous_date
2021-10-01	1
2021-10-02	1	2021-10-01
2021-10-02	1	2021-10-01
2021-10-09	1	2021-10-02
2021-10-15	1	2021-10-09
2021-10-01	2
2021-10-01	2
2021-10-04	2	2021-10-01
2021-10-04	2	2021-10-01
2021-10-04	2	2021-10-01
2021-10-11	2	2021-10-04
2021-10-11	2	2021-10-04

感谢您的帮助！

Answer 1

结合使用 LAG 函数，我们可以尝试：

WITH cte AS (
    SELECT *, LAG(current_date) OVER
                  (PARTITION BY user_id ORDER BY current_date) previous_date
    FROM (SELECT DISTINCT current_date, user_id FROM yourTable) t
)

SELECT t1.current_date, t1.user_id, t2.previous_date
FROM yourTable t1
INNER JOIN cte t2
    ON t2.user_id = t1.user_id AND t2.current_date = t1.current_date
ORDER BY t1.user_id, t1.current_date;

这是 SQL 服务器中的一个 demo，尽管相同的查询在 Presto 中应该运行需要最少的修改。

添加具有先前日期的列（不等于当前日期）[SQL，PrestoDB]

Add column with previous date (not equal current date)[SQL, PrestoDB]

sql

presto