时间戳的函数中

Posted 2023-03-20

参考技术A

Unix时间戳(Unix timestamp)，或称Unix时间(Unix time)、POSIX时间(POSIX time)，是一种时间表示方式，定义为从格林威治时间1970年01月01日00时00分00秒(北京时间1970年01月01日08时00分00秒)起至现在的总秒数。Unix时间戳不仅被使用在Unix系统、类Unix系统中(比如Linux系统)，也在许多其他操作系统中被广泛采用。
php中获取时间戳的方法是：time();Date();
Linux中获取时间戳的方法是：date +%s
Linux中将时间戳转换为日期： date -d "@<timestamp>"

比较两个时间戳的值，并根据 concat 函数中的预定义结构将它们插入结果中

【中文标题】比较两个时间戳的值，并根据 concat 函数中的预定义结构将它们插入结果中

【英文标题】：Compare values of two timestamps and insert them into results based on a pre-defined structure within a concat function

【发布时间】：2020-09-23 13:57:09

【问题描述】：

DB-Fiddle:

CREATE TABLE operations (
    id int auto_increment primary key,
    time_stamp DATE,
    product VARCHAR(255),
    plan_week VARCHAR(255),
    quantity INT
);

INSERT INTO operations
(time_stamp, product, plan_week, quantity
)
VALUES 
("2020-01-01", "Product_A", "CW01", "125"),
("2020-01-01", "Product_B", "CW01", "300"),
("2020-01-01", "Product_C", "CW08", "700"),
("2020-01-01", "Product_D", "CW01", "900"),
("2020-01-01", "Product_G", "CW05", "600"),

("2020-03-15", "Product_A", "CW01", "570"),
("2020-03-15", "Product_C", "CW02", "150"),
("2020-03-15", "Product_E", "CW02", "325"),
("2020-03-15", "Product_G", "CW01", "482");

预期结果：

time_stamp     product     plan_week      quantity         plan_week_switch
2020-01-01     Product_A      CW01           125                  no
2020-03-15     Product_A      CW01           570                  no
2020-01-01     Product_B      CW01           300                  no
2020-01-01     Product_C      CW08           700              CW08-to-CW02
2020-03-15     Product_C      CW02           150              CW08-to-CW02
2020-01-01     Product_D      CW01           900                  no
2020-03-15     Product_E      CW02           325                  no
2020-01-01     Product_G      CW05           600              CW05-to-CW01
2020-03-15     Product_G      CW01           482              CW05-to-CW01

---

在上表中，我比较了两个timestamps 并检查plan_week 是否在两个timestamps 之间切换。 如果是，我希望在plan_week_switch 列中描述它从哪个plan_week 到哪个plan_week 已更改。

目前，我正在使用这个查询：

SELECT 
time_stamp,
product,
plan_week,
quantity,

 (CASE WHEN MIN(plan_week) over (PARTITION BY product) = MAX(plan_week) over (PARTITION BY product)
 THEN 'no' ELSE CONCAT(CAST(MIN(plan_week) over (PARTITION by product) AS CHAR), '-to-',
 MAX(plan_week) over (PARTITION BY product)) END) AS plan_week_switch

FROM operations
GROUP BY 1,2
ORDER BY 2,1;

问题是在Product_G 的情况下，此查询将CW01-to-CW05 而不是CW05-to-CW01 插入列plan_week_switch. 但是，我总是希望 年长者 timestamp 显示为第一周，年轻 timestamp 周显示为第二周。

我需要在查询中进行哪些更改才能实现此目的？

【问题讨论】：

不是有一个产品连续切换3次以上的情况吗？

没有。每个产品的每个时间戳都恰好分配了一周。因此，只能有两个开关。

那么Akina的回答就可以了。

【参考方案1】：

WITH cte AS ( SELECT time_stamp,
                     product,
                     plan_week,
                     quantity,
                     FIRST_VALUE(plan_week) OVER (PARTITION BY product ORDER BY time_stamp DESC) first_plan,
                     FIRST_VALUE(plan_week) OVER (PARTITION BY product ORDER BY time_stamp ASC) last_plan
              FROM operations )
SELECT time_stamp,
       product,
       plan_week,
       quantity,
       CASE WHEN first_plan = last_plan
            THEN 'no'
            ELSE CONCAT(first_plan, '-to-', last_plan) 
            END plan_week_switch
FROM cte;

fiddle

查询仍然为 Product_G 插入 CW01-to-CW05 而不是 CW05-to-CW01

使用后向窗口定义：

WITH cte AS ( SELECT time_stamp,
                     product,
                     plan_week,
                     quantity,
                     FIRST_VALUE(plan_week) OVER (PARTITION BY product ORDER BY time_stamp ASC) first_plan,
                     FIRST_VALUE(plan_week) OVER (PARTITION BY product ORDER BY time_stamp DESC) last_plan
              FROM operations )
SELECT time_stamp,
       product,
       plan_week,
       quantity,
       CASE WHEN first_plan = last_plan
            THEN 'no'
            ELSE CONCAT(first_plan, '-to-', last_plan) 
            END plan_week_switch
FROM cte;

fiddle

【讨论】：

查询仍然为 Product_G 插入 CW01-to-CW05 而不是 CW05-to-CW01

@Michi 在窗口定义中交换 ASC 和 DESC 如果顺序错误。

仅用于我自己的文档：dbfiddle.uk/…

也用于我自己的文档：dbfiddle.uk/…