SQL：如何选择每天每个组的最大值？

Question

比方说，我有以下几列的表...

Name, Date, Number 

，说我们已经插入到这些列中的以下数据...

Bob, 2011-11-22, 1 
Bob, 2011-11-22, 5 
Bob, 2011-11-22, 4 
Bob, 2011-11-22, 3 
Wendy, 2011-11-22, 3 
Wendy, 2011-11-22, 4 
Wendy, 2011-11-22, 2 
Wendy, 2011-11-22, 1 
Chris, 2011-11-22, 4 
Chris, 2011-11-22, 1 
Bob, 2011-11-21, 4 
Bob, 2011-11-21, 3 
Wendy, 2011-11-21, 2 
Wendy, 2011-11-21, 4 
Wendy, 2011-11-21, 1 
Chris, 2011-11-21, 4 
Chris, 2011-11-21, 1 

现在想什么，我要做的是获得每个名称的最大数值，为每个日期。所以我的查询结果看起来像这样...

Bob, 2011-11-22, 5 
Wendy, 2011-11-22, 4 
Chris, 2011-11-22, 4 
Bob, 2011-11-21, 4 
Wendy, 2011-11-21, 4 
Chris, 2011-11-21, 4 

任何帮助，将不胜感激。我使用的是SQL 2005

Answer 1

SELECT Name, `Date`, MAX(Number) 
FROM yourtable 
GROUP BY Name, `Date` 

Answer 2

什么

SELECT [Name], [Date], MAX(Number) 
FROM [yourTable] 
GROUP BY [Name], [Date] 

参见：

• GROUP BY (Aggregate) Functions
• MySQL GROUP BY - Aggregate Functions

Answer 3

SELECT Name, Date, MAX(Number) 
    FROM YourTable 
    GROUP BY Name, Date; 

Answer 4

这不像你想象的那么难。

select name, date, max(number) from table group by name, date