SQL查询1天中每小时数据

Question

一个表,字段2个，id，created。id自增，created就是发表的日期，我做的是统计，统计每小时各发布多少。我现在用的是笨方法，for循环形式的，现在想知道SQL查询的方法 for (int i = 0; i < 24;i++ )
                {
                    where = new StringBuilder("1=1");
                    if (i == 23)
                    {
                        where.Append(" and created between '" + today + " " + i + ":0:0' and '" + today + " " + i + ":59:59'");                        
                        dt = info.QueryTable(list, where.ToString(), " id");
                        if (dt != null && dt.Rows.Count != 0)
                        {
                            hoursum[i] = dt.Rows.Count.ToString();
                        }
                        else
                        {
                            hoursum[i] = "0";
                        }
                    }
                    else 
                    {
                        where.Append(" and created between '" + today + " " + i + ":0:0' and '" + today + " " + (i + 1) + ":0:0'");
                        dt = info.QueryTable(list, where.ToString(), " id");
                        if (dt != null && dt.Rows.Count != 0)
                        {
                            hoursum[i] = dt.Rows.Count.ToString();
                        }
                        else
                        {
                            hoursum[i] = "0";
                        }
                    }
                }

Answer 1

SELECT COUNT(*) AS [item], [t1].[value] AS [key]
FROM (
    SELECT DATEPART(Hour, [t0].[日期]) AS [value]
    FROM [表名] AS [t0]
    ) AS [t1]
GROUP BY [t1].[value]

Answer 2

select datepart(hh,created) 小时,
count(1) 今天发布数量 
from 你的表
where convert(varchar(8),created,112)=convert(varchar(8),getdate(),112)
group by datepart(hh,created);

Answer 3

SELECT 
SUBSTRING(CONVERT(VARCHAR,created,120),0,14) AS '时间',
COUNT(1) AS '数量' 
FROM tablename
GROUP BY 
SUBSTRING(CONVERT(VARCHAR,DATE,120),0,14)