问题描述
我使用的是 SQL Server 2008.
I am using SQL Server 2008.
我想编写一个查询，提供给定天数的总活动量.具体来说，我想统计过去 7 天每天的总票数.
I want to write a query that gives me total activity for a number of given days. Specifically, I want to count total votes per day for the last seven days.
我的桌子是这样的:
VoteID --- VoteDate -------------- Vote --- BikeID
1 2012-01-01 08:24:25 1 1234
2 2012-01-01 08:24:25 0 5678
3 2012-01-02 08:24:25 1 1289
4 2012-01-03 08:24:25 0 1234
5 2012-01-04 08:24:25 1 5645
6 2012-01-05 08:24:25 0 1213
7 2012-01-06 08:24:25 1 1234
8 2012-01-07 08:24:25 0 1125
我需要我的结果看起来像这样
I need my results to look like this
VoteDate ---- Total
2012-01-01 5
2012-01-02 6
2012-01-03 7
2012-01-04 1
2012-01-05 3
我的想法是我必须做这样的事情:
My thought is that I have to do something like this:
SELECT SUM(CASE WHEN Vote = 1 THEN 1 ELSE 0 END) AS Total
FROM Votes
GROUP BY VoteDate
此查询不起作用，因为它仅计算(几乎完全相同)同时发生的投票.当然，我只想看特定的一天.我该如何实现?
This query doesn't work because it counts only votes that occurred (almost exactly) at the same time. Of course, I want to look only at a specific day. How do I make this happen?
推荐答案
Cast it as a date:
Cast it as a date:
SELECT
cast(VoteDate as date) as VoteDate,
SUM(CASE WHEN Vote = 1 THEN 1 ELSE 0 END) AS Total
FROM Votes
WHERE VoteDate between dateadd(day, -7, GETDATE()) and GETDATE()
GROUP BY cast(VoteDate as date)
您的 VoteDate 列是一个 datetime，但您只需要其中的 date 部分.最简单的方法是将其转换为 date 类型.您可以在此处阅读有关 SQL Server 日期类型的更多信息.
Your VoteDate column is a datetime, but you just want the date part of it. The easiest way to do that is to cast it as a date type. You can read more about SQL Server date types here.
如果你的 Vote 列是 1 或 0，你可以只做 sum(vote) as Total 而不是做 case声明.
And if your Vote column is either 1 or 0, you can just do sum(vote) as Total instead of doing the case statement.
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