将日期时间值向下舍入到最接近的半小时
我需要将 datetime2 值四舍五入到最接近的半小时.例如 '10/17/2013 12:10:00.123' 将向下舍入为 '10/17/2013 12:00:00.0' 而 '10/17/2013 12:34:17.123' 将向下舍入为 10/17/2013 12:30:00.0'.我的第一个想法是创建一个 UDF，它将日期和时间分开并这样做.但是，我想知道这样的事情是否可以在单个 T-SQL 语句中完成?
I have a requirement to round a datetime2 value down to the nearest half hour. For example '10/17/2013 12:10:00.123' would round down to '10/17/2013 12:00:00.0' And '10/17/2013 12:34:17.123' would round down to 10/17/2013 12:30:00.0'. My first thought was to create a UDF which would break the date and time apart and do it that way. However, I'm wondering if something like this can be done in a single T-SQL statement?
我使用的是 SQL Server 2012，列的数据类型是 dateTime2(不能转换为浮点数！！)
I'm using SQL Server 2012 and the data type of the column is a dateTime2 (which cannot be converted to a float!!)
Ian 的回答很好，但它包含了不必要的转换.我建议
The answer by Ian is good, but it contains an unnecessary conversion. I suggest
SELECT CONVERT(smalldatetime, ROUND(CAST([columnname] AS float) * 48.0,0,1)/48.0) FROM [tableName]
如果您想四舍五入到最接近的半小时而不是总是四舍五入，请使用
If you want to round to the nearest half-hour instead of always rounding down, use
SELECT CONVERT(smalldatetime, ROUND(CAST([columnname] AS float) * 48.0,0)/48.0) FROM [tableName]