【转】SQL Server 日期算法

 一周的第一天 select @@DATEFIRST 一个月的第一天 select dateadd (mm, datediff (mm, 0 , getdate ()), 0 ) 本周的星期一 select dateadd (wk, datediff (wk, 0 , getdate ()), 0 ) 一年的第一天 SELECT DATEADD (yy, DATEDIFF (yy, 0 , getdate ()), 0 ) 季度的第一天 SELECT DATEADD (qq, DATEDIFF (qq, 0 , getdate ()), 0 ) 当天的零时 SELECT DATEADD (dd, DATEDIFF (dd, 0 , getdate ()), 0 ) 上个月的最后一天 ：本月第一天减2ms. SELECT dateadd (ms, - 2 , DATEADD (mm, DATEDIFF (mm, 0 , getdate ()), 0 )) 本月的最后一天 SELECT dateadd (ms, - 2 , DATEADD (mm, DATEDIFF (m, 0 , getdate ()) + 1 , 0 )) 本月的第一个星期一 去掉时分秒 DATEADD ( day , DATEDIFF ( day , 0 , getdate ()), 0 ) 显示星期几 select datename (weekday, getdate ()) 如何取得某个月的天数 SELECT Day ( dateadd (ms, - 3 , DATEADD (mm, DATEDIFF (m, 0 , getdate ()) + 1 , 0 ))) 判断是否闰年： SELECT case day ( dateadd (mm, 2 , dateadd (ms, - 3 , DATEADD (yy, DATEDIFF (yy, 0 , getdate ()), 0 )))) when 28 then ' 平年 ' else ' 闰年 ' end 一个季度多少天 declare @m tinyint , @time smalldatetime select @m = month ( getdate ()) select @m = case when @m between 1 and 3 then 1 when @m between 4 and 6 then 4 when @m between 7 and 9 then 7 else 10 end select @time = datename ( year , getdate ()) + ' - ' + convert ( varchar ( 10 ), @m ) + ' -01 ' select datediff ( day , @time , dateadd (mm, 3 , @time ))