如何使用 Update in Case 语句和列作为别名-PHP中文网问答

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如何使用 Update in Case 语句和列作为别名

P粉214089349 2023-09-05 17:54:59

458

我有一个名为 sales_data 的表，其中有 3 列（id int、udf varchar(20)、date_of_sale datetime）。我试图通过将时间调整为 6 小时来查找 date_of_sale 列的工作日，现在我必须将 udf 列更新为与 date_of_sale 对应的工作日。我有一个选择查询的想法，但如何更新 udf 列？

select weekday(subtime(s.date_of_sale ,'6:0:0')) as putdata, CASE WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=0 THEN 'Sunday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=1 THEN 'Monday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=2 THEN 'Tuesday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=3 THEN 'Wednesday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=4 THEN 'Thursday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=5 THEN 'Friday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=6 THEN 'Saturday' END as udf from sales_data s;

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P粉2564870772023-09-06 14:26:54 2 楼

添加生成列（https://dev.mysql.com/doc/refman/8.0/en/create-table- generated-columns.html）以简化处理，并避免数据不一致：

alter table sales_data add weekday varchar(10) GENERATED ALWAYS AS (CASE WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=0 THEN 'Sunday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=1 THEN 'Monday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=2 THEN 'Tuesday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=3 THEN 'Wednesday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=4 THEN 'Thursday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=5 THEN 'Friday' WHEN weekday(subtime(s.date_of_sale ,'6:0:0'))=6 THEN 'Saturday' END );

查看演示：https://dbfiddle.uk/2d5iIvBv

（我没有得到相同的工作日，也许是区域设置？）

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P粉0356005552023-09-06 14:04:15 1 楼

您的上述查询已经差不多了。您只需要添加更新语句即可。

下面的查询应该适合您。

update sales_data set udf = case when weekday(subtime(date_of_sale,'6:0:0')) = 0 then 'Sunday' when weekday(subtime(date_of_sale,'6:0:0')) = 1 then 'Monday' when weekday(subtime(date_of_sale,'6:0:0')) = 2 then 'Tuesday' when weekday(subtime(date_of_sale,'6:0:0')) = 3 then 'Wednesday' when weekday(subtime(date_of_sale,'6:0:0')) = 4 then 'Thursday' when weekday(subtime(date_of_sale,'6:0:0')) = 5 then 'Friday' when weekday(subtime(date_of_sale,'6:0:0')) = 6 then 'Saturday' end;

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