MySQL：有条件地对时间序列进行分组

Question

我正在尝试根据日期总数提供按日期、周或月分组的时间序列总和。例如，如果最多 30 天，则按日期分组；如果在 31 到 90 天之间，则按周分组；如果超过 90 天，则按月分组。

我已经通过以下查询得到了我需要的结果：

1. 按日期分组：

SELECT
    dtCreated,
    FROM_DAYS(TO_DAYS(dtCreated) -MOD(TO_DAYS(dtCreated) -1, 7)) as week_beginning,
    DATE(DATE_FORMAT(dtCreated, '%Y-%m-01')) AS month_beginning,
    COALESCE(SUM(valToSum), 0) as soma
    FROM(   
        SELECT 
            DATE(dt_created) as dtCreated,
            valToSum
        FROM MQV_PDV_TICKET
    ) as derived_table
GROUP BY dtCreated

2. 按周分组：

SELECT
    dtCreated,
    FROM_DAYS(TO_DAYS(dtCreated) -MOD(TO_DAYS(dtCreated) -1, 7)) as week_beginning,
    DATE(DATE_FORMAT(dtCreated, '%Y-%m-01')) AS month_beginning,
    COALESCE(SUM(valToSum), 0) as soma
    FROM(   
        SELECT 
            DATE(dt_created) as dtCreated,
            valToSum
        FROM MQV_PDV_TICKET
    ) as derived_table
GROUP BY week_beginning

3. 按月分组：

SELECT
    dtCreated,
    FROM_DAYS(TO_DAYS(dtCreated) -MOD(TO_DAYS(dtCreated) -1, 7)) as week_beginning,
    DATE(DATE_FORMAT(dtCreated, '%Y-%m-01')) AS month_beginning,
    COALESCE(SUM(valToSum), 0) as soma
    FROM(   
        SELECT 
            DATE(dt_created) as dtCreated,
            valToSum
        FROM MQV_PDV_TICKET
    ) as derived_table
GROUP BY month_beginning

所有三个选项都工作得很好，并通过适当的分组为我带来正确的总和结果，但我无法使其动态分组，使其取决于总天数。

我已经尝试在

CASE WHEN

子句中使用

GROUP BY

，以这种方式：

GROUP BY (CASE 
             WHEN COUNT(*) <= 30 THEN dtCreated
             WHEN COUNT(*) BETWEEN 31 AND 90 THEN week_beginning
             WHEN COUNT(*) > 90 THEN month_beginning
         END)

但是它让我出错了：

#1111 - invalid use of group function  (GROUP)

如何实现这种条件分组？

提前谢谢！

Answer 1

我会使用WITH语句，在单独的查询中检查记录数，然后根据建议的条件对其进行分组。

WITH DateRange AS (
    SELECT
        MIN(DATE(dt_created)) AS start_date,
        MAX(DATE(dt_created)) AS end_date,
        COUNT(DISTINCT DATE(dt_created)) AS total_days
    FROM MQV_PDV_TICKET
),
PreparedData AS (
    SELECT
        DATE(dt_created) AS dtCreated,
        FROM_DAYS(TO_DAYS(dt_created) - MOD(TO_DAYS(dt_created) - 1, 7)) AS week_beginning,
        DATE_FORMAT(dt_created, '%Y-%m-01') AS month_beginning,
        valToSum
    FROM MQV_PDV_TICKET
)
SELECT
    CASE
        WHEN (SELECT total_days FROM DateRange) <= 30 THEN dtCreated
        WHEN (SELECT total_days FROM DateRange) BETWEEN 31 AND 90 THEN week_beginning
        ELSE month_beginning
    END AS grouping_period,
    COALESCE(SUM(valToSum), 0) AS total_sum
FROM PreparedData
GROUP BY grouping_period;