SQL（sqlite）表转置

Question

我在 sqlite 中有一张表

| id | Weekday   | reading_datetime |
|----+-----------+------------------|
|  1 | Sunday    | datetime_value_1 |
|  2 | monday    | datetime_value_2 |
|  3 | tuesday   | datetime_value_3 |
|  4 | wednesday | datetime_value_4 |
|  5 | thursday  | datetime_value_5 |
|  6 | friday    | datetime_value_6 |
|  7 | saturday  | datetime_value_7 |
|  8 | sunday    | datetime_value_8 |
|  9 | monday    | datetime_value_9 |
| .. | ..        | ..               |

一周中的每一天的表中都有几年的日期时间值 我想要的是转置七列中的值 像这样：

| sunday      | monday      | tuesday     | wednesday   | thursday    | friday      | saturday    |
|-------------+-------------+-------------+-------------+-------------+-------------+-------------|
| dt_value_1  | dt_value_2  | dt_value_3  | dt_value_4  | dt_value_5  | dt_value_6  | dt_value_7  |
| dt_value_8  | dt_value_9  | dt_value_10 | dt_value_11 | dt_value_12 | dt_value_13 | dt_value_14 |
| dt_value_15 | dt_value_16 | dt_value_17 | dt_value_18 | dt_value_19 | dt_value_20 | dt_value_21 |
| dt_value_22 | dt_value_23 | dt_value_24 | dt_value_25 | dt_value_26 | dt_value_27 | dt_value_28 |

有人可以帮忙吗？

Answer 1

假设一周中的每一天总是有每周记录，我们可以在

ROW_NUMBER

的帮助下尝试旋转方法：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY Weekday ORDER BY id) rn
    FROM yourTable
)

SELECT
    MAX(CASE WHEN Weekday = 'sunday'    THEN reading_datetime END) AS sunday,
    MAX(CASE WHEN Weekday = 'monday'    THEN reading_datetime END) AS monday,
    MAX(CASE WHEN Weekday = 'tuesday'   THEN reading_datetime END) AS tuesday,
    MAX(CASE WHEN Weekday = 'wednesday' THEN reading_datetime END) AS wednesday,
    MAX(CASE WHEN Weekday = 'thursday'  THEN reading_datetime END) AS thursday,
    MAX(CASE WHEN Weekday = 'friday'    THEN reading_datetime END) AS friday,
    MAX(CASE WHEN Weekday = 'saturday'  THEN reading_datetime END) AS saturday
FROM cte
GROUP BY (rn - 1) / 7
ORDER BY (rn - 1) / 7;