Question

我正在尝试使用此代码在3个时段对字段求和：

SELECT 
CASE when TIME(v.time) between cast('00:00:00' as time) and cast('06:00:00' as time) then '00:00:00 - 06:00:00'
when TIME(v.time) between cast('06:00:00' as time) and cast('16:00:00' as time) then '06:00:00 - 16:00:00'
when TIME(v.time) between cast('16:00:00' as time) and cast('00:00:00' as time) then '16:00:00 - 00:00:00' End as 'TimeSlot',
sum(v.resting)
FROM vital_activity_histogram v
GROUP BY 'TimeSlot'

我想要的结果是（例如）：

time slot              | Sum(v.resting)
00:00:00 - 06:00:00        24
06:00:00 - 16:00:00        56
16:00:00 - 00:00:00        72

运行查询时得到的是：

time slot              | Sum(v.resting)
00:00:00 - 06:00:00        24

我在其他时段内有数据。有人知道怎么修这个东西吗？谢谢！

Answer 1

您需要GROUP BY TimeSlot，而不是GROUP BY 'TimeSlot'：因为您需要对字符串文字进行分组，这是常量（因此每个记录都在同一个组中）。

另见When to use single quotes, double quotes, and backticks in MySQL

在MySql中使用Case的时隙

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