GROUP BY DATEADD(day, DATEDIFF(day, 0, MyDateTimeColumn), 0)

或者在SQL Server 2008以后，你可以像@Oded建议的那样简单地转换为Date:

GROUP BY CAST(orderDate AS DATE)

在Sql 2008之前，通过去掉日期部分:

GROUP BY CONVERT(CHAR(8),DateTimeColumn,10)

下面是我使用的一个例子，当我需要计算特定日期的记录数量而不包括时间部分时:

select count(convert(CHAR(10), dtcreatedate, 103) ),convert(char(10), dtcreatedate, 103)
FROM dbo.tbltobecounted
GROUP BY CONVERT(CHAR(10),dtcreatedate,103)
ORDER BY CONVERT(CHAR(10),dtcreatedate,103)

将值转换为组的日期类型。

GROUP BY CAST(myDateTime AS DATE)

GROUP BY DATEADD(day, DATEDIFF(day, 0, MyDateTimeColumn), 0)

或者在SQL Server 2008以后，你可以像@Oded建议的那样简单地转换为Date:

GROUP BY CAST(orderDate AS DATE)

下面的例子在oracle中工作得很好

select to_char(columnname, 'DD/MON/yyyy'), count(*) from table_name group by to_char(createddate, 'DD/MON/yyyy');