sql如何取某年某月的第一天和最后一天
SELECT CAST((LEFT('20093',4)+'-'+SUBSTRING('20093',5,LEN('20093'))+'-'+'01') AS DATETIME)
--第一天
SELECT DATEADD(DAY,-1,DATEADD(MONTH,1,CAST((LEFT('20093',4)+'-'+SUBSTRING('20093',5,LEN('20093'))+'-'+'01') AS DATETIME)))
--最后一天
原理：第一天肯定是1号拉 ，最后一天是下个月第一天减一天
【数据所在服务器】本月的第一天和最后一天：
SELECT dateadd(ms,-1,DATEADD(mm, DATEDIFF(m,0,getdate()), 0)) as mouthfirstdate,dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+1, 0)) as mouthlastdate
===============================最后一天=====================================
本月【数据所在服务器】最后一天：
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+1, 0)) as mouthlastdate
下月【数据所在服务器】最后一天：
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+2, 0)) as mouthlastdate
下下月【数据所在服务器】最后一天：
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+3, 0)) as mouthlastdate
下下下月【数据所在服务器】最后一天：
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+4, 0)) as mouthlastdate
下下下月【数据所在服务器】最后一天：
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+5, 0)) as mouthlastdate
下下下下月【数据所在服务器】最后一天：
SELECT dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+6, 0)) as mouthlastdate
===============================第一天=====================================
本月第一天
SELECT dateadd(ms,-1,DATEADD(mm, DATEDIFF(m,0,getdate()), 0)) as mouthlastdate
下月第一天：
SELECT dateadd(ms,-1,DATEADD(mm, DATEDIFF(m,0,getdate())+1, 0)) as mouthlastdate
下下月第一天：
SELECT dateadd(ms,-1,DATEADD(mm, DATEDIFF(m,0,getdate())+2, 0)) as mouthlastdate